diff --git a/packages/react-cache/src/ReactCacheOld.js b/packages/react-cache/src/ReactCacheOld.js
index edd75e5861c64..3661df00ca907 100644
--- a/packages/react-cache/src/ReactCacheOld.js
+++ b/packages/react-cache/src/ReactCacheOld.js
@@ -122,7 +122,6 @@ function accessResult<I, K, V>(
     );
     const newResult: PendingResult = {
       status: Pending,
-      // $FlowFixMe[method-unbinding]
       value: thenable,
     };
     // $FlowFixMe[escaped-generic] discovered when updating Flow
diff --git a/packages/react-client/src/ReactFlightClient.js b/packages/react-client/src/ReactFlightClient.js
index 33db1c494b2d9..44815dce4b5b9 100644
--- a/packages/react-client/src/ReactFlightClient.js
+++ b/packages/react-client/src/ReactFlightClient.js
@@ -321,7 +321,6 @@ function initializeModelChunk<T>(chunk: ResolvedModelChunk<T>): void {
       initializingChunkBlockedModel !== null &&
       initializingChunkBlockedModel.deps > 0
     ) {
-      // $FlowFixMe[incompatible-type]: found when upgrading Flow
       initializingChunkBlockedModel.value = value;
       // We discovered new dependencies on modules that are not yet resolved.
       // We have to go the BLOCKED state until they're resolved.
diff --git a/packages/react-devtools-shared/src/backend/NativeStyleEditor/setupNativeStyleEditor.js b/packages/react-devtools-shared/src/backend/NativeStyleEditor/setupNativeStyleEditor.js
index fee2847f05e6d..22b9e74850e87 100644
--- a/packages/react-devtools-shared/src/backend/NativeStyleEditor/setupNativeStyleEditor.js
+++ b/packages/react-devtools-shared/src/backend/NativeStyleEditor/setupNativeStyleEditor.js
@@ -129,7 +129,6 @@ function measureStyle(
     return;
   }
 
-  // $FlowFixMe the parameter types of an unknown function are unknown
   instance.measure((x, y, width, height, left, top) => {
     // RN Android sometimes returns undefined here. Don't send measurements in this case.
     // https://github.com/jhen0409/react-native-debugger/issues/84#issuecomment-304611817
diff --git a/packages/react-devtools-shared/src/backend/console.js b/packages/react-devtools-shared/src/backend/console.js
index 0ca957f216c6f..025180b872dae 100644
--- a/packages/react-devtools-shared/src/backend/console.js
+++ b/packages/react-devtools-shared/src/backend/console.js
@@ -181,7 +181,6 @@ export function patch({
     unpatchFn = () => {
       for (const method in originalConsoleMethods) {
         try {
-          // $FlowFixMe property error|warn is not writable.
           targetConsole[method] = originalConsoleMethods[method];
         } catch (error) {}
       }
@@ -279,7 +278,6 @@ export function patch({
         overrideMethod.__REACT_DEVTOOLS_ORIGINAL_METHOD__ = originalMethod;
         originalMethod.__REACT_DEVTOOLS_OVERRIDE_METHOD__ = overrideMethod;
 
-        // $FlowFixMe property error|warn is not writable.
         targetConsole[method] = overrideMethod;
       } catch (error) {}
     });
@@ -321,7 +319,6 @@ export function patchForStrictMode() {
     unpatchForStrictModeFn = () => {
       for (const method in originalConsoleMethods) {
         try {
-          // $FlowFixMe property error|warn is not writable.
           targetConsole[method] = originalConsoleMethods[method];
         } catch (error) {}
       }
@@ -355,7 +352,6 @@ export function patchForStrictMode() {
         overrideMethod.__REACT_DEVTOOLS_STRICT_MODE_ORIGINAL_METHOD__ = originalMethod;
         originalMethod.__REACT_DEVTOOLS_STRICT_MODE_OVERRIDE_METHOD__ = overrideMethod;
 
-        // $FlowFixMe property error|warn is not writable.
         targetConsole[method] = overrideMethod;
       } catch (error) {}
     });
diff --git a/packages/react-devtools-shared/src/backend/profilingHooks.js b/packages/react-devtools-shared/src/backend/profilingHooks.js
index c91bb36a16148..5cadc175e4bfc 100644
--- a/packages/react-devtools-shared/src/backend/profilingHooks.js
+++ b/packages/react-devtools-shared/src/backend/profilingHooks.js
@@ -53,7 +53,6 @@ let supportsUserTimingV3 = false;
 if (supportsUserTiming) {
   const CHECK_V3_MARK = '__v3';
   const markOptions = {};
-  // $FlowFixMe: Ignore Flow complaining about needing a value
   Object.defineProperty(markOptions, 'startTime', {
     get: function() {
       supportsUserTimingV3 = true;
diff --git a/packages/react-devtools-shared/src/backend/renderer.js b/packages/react-devtools-shared/src/backend/renderer.js
index 4e9dbb3156c1c..bcf3d94ecca8c 100644
--- a/packages/react-devtools-shared/src/backend/renderer.js
+++ b/packages/react-devtools-shared/src/backend/renderer.js
@@ -387,7 +387,6 @@ export function getInternalReactConstants(
     const symbolOrNumber =
       typeof type === 'object' && type !== null ? type.$$typeof : type;
 
-    // $FlowFixMe Flow doesn't know about typeof "symbol"
     return typeof symbolOrNumber === 'symbol'
       ? // $FlowFixMe `toString()` doesn't match the type signature?
         symbolOrNumber.toString()
@@ -3275,7 +3274,6 @@ export function attach(
       for (const method in console) {
         try {
           originalConsoleMethods[method] = console[method];
-          // $FlowFixMe property error|warn is not writable.
           console[method] = () => {};
         } catch (error) {}
       }
@@ -3290,7 +3288,6 @@ export function attach(
         // Restore original console functionality.
         for (const method in originalConsoleMethods) {
           try {
-            // $FlowFixMe property error|warn is not writable.
             console[method] = originalConsoleMethods[method];
           } catch (error) {}
         }
@@ -3713,7 +3710,6 @@ export function attach(
       id,
       responseID: requestID,
       type: 'full-data',
-      // $FlowFixMe[incompatible-return] found when upgrading Flow
       // $FlowFixMe[prop-missing] found when upgrading Flow
       value: cleanedInspectedElement,
     };
diff --git a/packages/react-devtools-shared/src/backend/views/Highlighter/index.js b/packages/react-devtools-shared/src/backend/views/Highlighter/index.js
index 3005f2481be06..4717db95162d4 100644
--- a/packages/react-devtools-shared/src/backend/views/Highlighter/index.js
+++ b/packages/react-devtools-shared/src/backend/views/Highlighter/index.js
@@ -119,7 +119,6 @@ export default function setupHighlighter(
       if (scrollIntoView && typeof node.scrollIntoView === 'function') {
         // If the node isn't visible show it before highlighting it.
         // We may want to reconsider this; it might be a little disruptive.
-        // $FlowFixMe Flow only knows about 'start' | 'end'
         node.scrollIntoView({block: 'nearest', inline: 'nearest'});
       }
 
diff --git a/packages/react-devtools-shared/src/devtools/cache.js b/packages/react-devtools-shared/src/devtools/cache.js
index b0a01a443845a..8cc902d95f2a0 100644
--- a/packages/react-devtools-shared/src/devtools/cache.js
+++ b/packages/react-devtools-shared/src/devtools/cache.js
@@ -128,7 +128,6 @@ function accessResult<Input, Key, Value>(
     );
     const newResult: PendingResult = {
       status: Pending,
-      // $FlowFixMe[method-unbinding]
       value: thenable,
     };
     entriesForResource.set(key, newResult);
diff --git a/packages/react-devtools-shared/src/devtools/views/Components/InspectedElementHooksTree.js b/packages/react-devtools-shared/src/devtools/views/Components/InspectedElementHooksTree.js
index 27e7ec69ce0b0..ce781506463cf 100644
--- a/packages/react-devtools-shared/src/devtools/views/Components/InspectedElementHooksTree.js
+++ b/packages/react-devtools-shared/src/devtools/views/Components/InspectedElementHooksTree.js
@@ -138,7 +138,6 @@ export function InnerHooksTreeView({
   inspectedElement,
   path,
 }: InnerHooksTreeViewProps): React.Node {
-  // $FlowFixMe "Missing type annotation for U" whatever that means
   return hooks.map((hook, index) => (
     <HookView
       key={index}
@@ -356,7 +355,6 @@ function HookView({
               className={name !== '' ? styles.Name : styles.NameAnonymous}>
               {hookDisplayName || 'Anonymous'}
             </span>{' '}
-            {/* $FlowFixMe */}
             <span className={styles.Value} onClick={toggleIsOpen}>
               {displayValue}
             </span>
diff --git a/packages/react-devtools-shared/src/devtools/views/Components/Tree.js b/packages/react-devtools-shared/src/devtools/views/Components/Tree.js
index 089d98ecebadb..64c779c2f2f51 100644
--- a/packages/react-devtools-shared/src/devtools/views/Components/Tree.js
+++ b/packages/react-devtools-shared/src/devtools/views/Components/Tree.js
@@ -409,7 +409,6 @@ export default function Tree(props: Props): React.Node {
           tabIndex={0}>
           <AutoSizer>
             {({height, width}) => (
-              // $FlowFixMe https://github.com/facebook/flow/issues/7341
               <FixedSizeList
                 className={styles.List}
                 height={height}
diff --git a/packages/react-devtools-shared/src/hook.js b/packages/react-devtools-shared/src/hook.js
index 3d65ca34c8316..547f6b35e63ab 100644
--- a/packages/react-devtools-shared/src/hook.js
+++ b/packages/react-devtools-shared/src/hook.js
@@ -250,7 +250,6 @@ export function installHook(target: any): DevToolsHook | null {
     unpatchFn = () => {
       for (const method in originalConsoleMethods) {
         try {
-          // $FlowFixMe property error|warn is not writable.
           targetConsole[method] = originalConsoleMethods[method];
         } catch (error) {}
       }
@@ -302,7 +301,6 @@ export function installHook(target: any): DevToolsHook | null {
         overrideMethod.__REACT_DEVTOOLS_STRICT_MODE_ORIGINAL_METHOD__ = originalMethod;
         originalMethod.__REACT_DEVTOOLS_STRICT_MODE_OVERRIDE_METHOD__ = overrideMethod;
 
-        // $FlowFixMe property error|warn is not writable.
         targetConsole[method] = overrideMethod;
       } catch (error) {}
     });
diff --git a/packages/react-devtools-shared/src/hooks/parseHookNames/parseSourceAndMetadata.js b/packages/react-devtools-shared/src/hooks/parseHookNames/parseSourceAndMetadata.js
index 15c3202b88457..ba3c1e096b67b 100644
--- a/packages/react-devtools-shared/src/hooks/parseHookNames/parseSourceAndMetadata.js
+++ b/packages/react-devtools-shared/src/hooks/parseHookNames/parseSourceAndMetadata.js
@@ -186,7 +186,6 @@ function findHookNames(
     }
 
     const key = getHookSourceLocationKey(hookSource);
-    // $FlowFixMe[incompatible-call] found when upgrading Flow
     map.set(key, name);
   });
 
diff --git a/packages/react-devtools-shared/src/inspectedElementMutableSource.js b/packages/react-devtools-shared/src/inspectedElementMutableSource.js
index 7c3704ee424fb..96021dd2ae25e 100644
--- a/packages/react-devtools-shared/src/inspectedElementMutableSource.js
+++ b/packages/react-devtools-shared/src/inspectedElementMutableSource.js
@@ -137,7 +137,6 @@ export function inspectElement({
 
         // A path has been hydrated.
         // Merge it with the latest copy we have locally and resolve with the merged value.
-        // $FlowFixMe[incompatible-type] found when upgrading Flow
         inspectedElement = inspectedElementCache.get(id) || null;
         if (inspectedElement !== null) {
           // Clone element
@@ -151,7 +150,6 @@ export function inspectElement({
             hydrateHelper(value, ((path: any): Path)),
           );
 
-          // $FlowFixMe[incompatible-call] found when upgrading Flow
           inspectedElementCache.set(id, inspectedElement);
 
           return [inspectedElement, type];
diff --git a/packages/react-devtools-shell/src/app/DeeplyNestedComponents/index.js b/packages/react-devtools-shell/src/app/DeeplyNestedComponents/index.js
index dda89a3cd48e6..8e172a3ae55b7 100644
--- a/packages/react-devtools-shell/src/app/DeeplyNestedComponents/index.js
+++ b/packages/react-devtools-shell/src/app/DeeplyNestedComponents/index.js
@@ -15,7 +15,6 @@ function wrapWithHoc(Component, index) {
     return <Component />;
   }
 
-  // $FlowFixMe
   const displayName = Component.displayName || Component.name;
 
   // $FlowFixMe[incompatible-type] found when upgrading Flow
diff --git a/packages/react-devtools-shell/src/app/ElementTypes/index.js b/packages/react-devtools-shell/src/app/ElementTypes/index.js
index d105bff9e1d05..c0e82bb925482 100644
--- a/packages/react-devtools-shell/src/app/ElementTypes/index.js
+++ b/packages/react-devtools-shell/src/app/ElementTypes/index.js
@@ -15,7 +15,6 @@ import {
   memo,
   Component,
   Fragment,
-  // $FlowFixMe Flow doesn't know about the Profiler import yet
   Profiler,
   StrictMode,
   Suspense,
diff --git a/packages/react-devtools-timeline/src/view-base/utils/normalizeWheel.js b/packages/react-devtools-timeline/src/view-base/utils/normalizeWheel.js
index 82fe9ec35c0ee..6e8a620b4e02e 100644
--- a/packages/react-devtools-timeline/src/view-base/utils/normalizeWheel.js
+++ b/packages/react-devtools-timeline/src/view-base/utils/normalizeWheel.js
@@ -71,17 +71,11 @@ export function normalizeWheel(event: WheelEvent): NormalizedWheelDelta {
   let deltaX = event.deltaX;
   let deltaY = event.deltaY;
 
-  if (
-    // $FlowFixMe DOM_DELTA_LINE missing from WheelEvent
-    event.deltaMode === WheelEvent.DOM_DELTA_LINE
-  ) {
+  if (event.deltaMode === WheelEvent.DOM_DELTA_LINE) {
     // delta in LINE units
     deltaX *= LINE_HEIGHT;
     deltaY *= LINE_HEIGHT;
-  } else if (
-    // $FlowFixMe DOM_DELTA_PAGE missing from WheelEvent
-    event.deltaMode === WheelEvent.DOM_DELTA_PAGE
-  ) {
+  } else if (event.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
     // delta in PAGE units
     deltaX *= PAGE_HEIGHT;
     deltaY *= PAGE_HEIGHT;
diff --git a/packages/react-dom-bindings/src/client/ReactDOMComponent.js b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
index 17255b9fcc80d..25e37d01c2210 100644
--- a/packages/react-dom-bindings/src/client/ReactDOMComponent.js
+++ b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
@@ -419,7 +419,6 @@ export function createElement(
       const firstChild = ((div.firstChild: any): HTMLScriptElement);
       domElement = div.removeChild(firstChild);
     } else if (typeof props.is === 'string') {
-      // $FlowFixMe `createElement` should be updated for Web Components
       domElement = ownerDocument.createElement(type, {is: props.is});
     } else {
       // Separate else branch instead of using `props.is || undefined` above because of a Firefox bug.
diff --git a/packages/react-dom-bindings/src/events/checkPassiveEvents.js b/packages/react-dom-bindings/src/events/checkPassiveEvents.js
index 396060867414b..b67e87277d2e4 100644
--- a/packages/react-dom-bindings/src/events/checkPassiveEvents.js
+++ b/packages/react-dom-bindings/src/events/checkPassiveEvents.js
@@ -16,7 +16,6 @@ export let passiveBrowserEventsSupported: boolean = false;
 if (canUseDOM) {
   try {
     const options = {};
-    // $FlowFixMe: Ignore Flow complaining about needing a value
     Object.defineProperty(options, 'passive', {
       get: function() {
         passiveBrowserEventsSupported = true;
diff --git a/packages/react-dom-bindings/src/events/plugins/BeforeInputEventPlugin.js b/packages/react-dom-bindings/src/events/plugins/BeforeInputEventPlugin.js
index a4554f6c9213a..d00e22b3bab69 100644
--- a/packages/react-dom-bindings/src/events/plugins/BeforeInputEventPlugin.js
+++ b/packages/react-dom-bindings/src/events/plugins/BeforeInputEventPlugin.js
@@ -227,10 +227,8 @@ function extractCompositionEvent(
     }
   }
 
-  // $FlowFixMe[incompatible-call] found when upgrading Flow
   const listeners = accumulateTwoPhaseListeners(targetInst, eventType);
   if (listeners.length > 0) {
-    // $FlowFixMe[incompatible-type]
     const event: ReactSyntheticEvent = new SyntheticCompositionEvent(
       eventType,
       domEventName,
@@ -403,7 +401,6 @@ function extractBeforeInputEvent(
 
   const listeners = accumulateTwoPhaseListeners(targetInst, 'onBeforeInput');
   if (listeners.length > 0) {
-    // $FlowFixMe[incompatible-type]
     const event: ReactSyntheticEvent = new SyntheticInputEvent(
       'onBeforeInput',
       'beforeinput',
diff --git a/packages/react-dom-bindings/src/events/plugins/ChangeEventPlugin.js b/packages/react-dom-bindings/src/events/plugins/ChangeEventPlugin.js
index cc99bd3ad1264..d4e397c3e9805 100644
--- a/packages/react-dom-bindings/src/events/plugins/ChangeEventPlugin.js
+++ b/packages/react-dom-bindings/src/events/plugins/ChangeEventPlugin.js
@@ -59,7 +59,6 @@ function createAndAccumulateChangeEvent(
   enqueueStateRestore(((target: any): Node));
   const listeners = accumulateTwoPhaseListeners(inst, 'onChange');
   if (listeners.length > 0) {
-    // $FlowFixMe[incompatible-type]
     const event: ReactSyntheticEvent = new SyntheticEvent(
       'onChange',
       'change',
diff --git a/packages/react-dom-bindings/src/events/plugins/EnterLeaveEventPlugin.js b/packages/react-dom-bindings/src/events/plugins/EnterLeaveEventPlugin.js
index 4183b8785620a..29484a5cd5118 100644
--- a/packages/react-dom-bindings/src/events/plugins/EnterLeaveEventPlugin.js
+++ b/packages/react-dom-bindings/src/events/plugins/EnterLeaveEventPlugin.js
@@ -104,7 +104,6 @@ function extractEvents(
       const nearestMounted = getNearestMountedFiber(to);
       if (
         to !== nearestMounted ||
-        // $FlowFixMe[incompatible-use] found when upgrading Flow
         (to.tag !== HostComponent && to.tag !== HostText)
       ) {
         to = null;
@@ -135,8 +134,6 @@ function extractEvents(
   const fromNode = from == null ? win : getNodeFromInstance(from);
   const toNode = to == null ? win : getNodeFromInstance(to);
 
-  // $FlowFixMe[prop-missing]
-  // $FlowFixMe[incompatible-type]
   const leave: KnownReactSyntheticEvent = new SyntheticEventCtor(
     leaveEventType,
     eventTypePrefix + 'leave',
@@ -153,7 +150,6 @@ function extractEvents(
   // the first ancestor. Next time, we will ignore the event.
   const nativeTargetInst = getClosestInstanceFromNode((nativeEventTarget: any));
   if (nativeTargetInst === targetInst) {
-    // $FlowFixMe[prop-missing]
     const enterEvent: KnownReactSyntheticEvent = new SyntheticEventCtor(
       enterEventType,
       eventTypePrefix + 'enter',
diff --git a/packages/react-dom-bindings/src/events/plugins/SelectEventPlugin.js b/packages/react-dom-bindings/src/events/plugins/SelectEventPlugin.js
index 2032b02565329..950b505fe9961 100644
--- a/packages/react-dom-bindings/src/events/plugins/SelectEventPlugin.js
+++ b/packages/react-dom-bindings/src/events/plugins/SelectEventPlugin.js
@@ -116,7 +116,6 @@ function constructSelectEvent(dispatchQueue, nativeEvent, nativeEventTarget) {
       'onSelect',
     );
     if (listeners.length > 0) {
-      // $FlowFixMe[incompatible-type]
       const event: ReactSyntheticEvent = new SyntheticEvent(
         'onSelect',
         'select',
diff --git a/packages/react-dom-bindings/src/events/plugins/SimpleEventPlugin.js b/packages/react-dom-bindings/src/events/plugins/SimpleEventPlugin.js
index 07c9ec94c7104..78df13154b364 100644
--- a/packages/react-dom-bindings/src/events/plugins/SimpleEventPlugin.js
+++ b/packages/react-dom-bindings/src/events/plugins/SimpleEventPlugin.js
@@ -173,7 +173,6 @@ function extractEvents(
     );
     if (listeners.length > 0) {
       // Intentionally create event lazily.
-      // $FlowFixMe[incompatible-type]
       const event: ReactSyntheticEvent = new SyntheticEventCtor(
         reactName,
         reactEventType,
@@ -206,7 +205,6 @@ function extractEvents(
     );
     if (listeners.length > 0) {
       // Intentionally create event lazily.
-      // $FlowFixMe[incompatible-type]
       const event: ReactSyntheticEvent = new SyntheticEventCtor(
         reactName,
         reactEventType,
diff --git a/packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js
index cedc935f7ac26..22429ac70d183 100644
--- a/packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js
@@ -511,7 +511,6 @@ function pushAttribute(
     // shouldRemoveAttribute
     switch (typeof value) {
       case 'function':
-      // $FlowFixMe symbol is perfectly valid here
       case 'symbol': // eslint-disable-line
         return;
       case 'boolean': {
@@ -620,7 +619,6 @@ function pushAttribute(
     // shouldRemoveAttribute
     switch (typeof value) {
       case 'function':
-      // $FlowFixMe symbol is perfectly valid here
       case 'symbol': // eslint-disable-line
         return;
       case 'boolean': {
diff --git a/packages/react-dom-bindings/src/shared/DOMProperty.js b/packages/react-dom-bindings/src/shared/DOMProperty.js
index c4ae688aff35f..5333e47db580c 100644
--- a/packages/react-dom-bindings/src/shared/DOMProperty.js
+++ b/packages/react-dom-bindings/src/shared/DOMProperty.js
@@ -123,7 +123,6 @@ export function shouldRemoveAttributeWithWarning(
   }
   switch (typeof value) {
     case 'function':
-    // $FlowFixMe symbol is perfectly valid here
     case 'symbol': // eslint-disable-line
       return true;
     case 'boolean': {
diff --git a/packages/react-fs/src/ReactFilesystem.js b/packages/react-fs/src/ReactFilesystem.js
index 2d376a4dca940..c47ca6f256959 100644
--- a/packages/react-fs/src/ReactFilesystem.js
+++ b/packages/react-fs/src/ReactFilesystem.js
@@ -121,7 +121,6 @@ export function access(path: string, mode?: number): void {
     record = createRecordFromThenable(thenable);
     accessCache.push(mode, record);
   }
-  // $FlowFixMe[incompatible-call] found when upgrading Flow
   readRecord(record); // No return value.
 }
 
diff --git a/packages/react-reconciler/src/ReactFiberAct.new.js b/packages/react-reconciler/src/ReactFiberAct.new.js
index fbb12f4bd178b..bdad7161f6518 100644
--- a/packages/react-reconciler/src/ReactFiberAct.new.js
+++ b/packages/react-reconciler/src/ReactFiberAct.new.js
@@ -40,7 +40,6 @@ export function isLegacyActEnvironment(fiber: Fiber): boolean {
 export function isConcurrentActEnvironment(): void | boolean {
   if (__DEV__) {
     const isReactActEnvironmentGlobal =
-      // $FlowFixMe – Flow doesn't know about IS_REACT_ACT_ENVIRONMENT global
       typeof IS_REACT_ACT_ENVIRONMENT !== 'undefined'
         ? IS_REACT_ACT_ENVIRONMENT
         : undefined;
diff --git a/packages/react-reconciler/src/ReactFiberAct.old.js b/packages/react-reconciler/src/ReactFiberAct.old.js
index 90f771b594059..7dc4eb7015b82 100644
--- a/packages/react-reconciler/src/ReactFiberAct.old.js
+++ b/packages/react-reconciler/src/ReactFiberAct.old.js
@@ -40,7 +40,6 @@ export function isLegacyActEnvironment(fiber: Fiber): boolean {
 export function isConcurrentActEnvironment(): void | boolean {
   if (__DEV__) {
     const isReactActEnvironmentGlobal =
-      // $FlowFixMe – Flow doesn't know about IS_REACT_ACT_ENVIRONMENT global
       typeof IS_REACT_ACT_ENVIRONMENT !== 'undefined'
         ? IS_REACT_ACT_ENVIRONMENT
         : undefined;
diff --git a/packages/react-reconciler/src/ReactFiberCommitWork.new.js b/packages/react-reconciler/src/ReactFiberCommitWork.new.js
index 4066f37b3b02a..7e489ccfe74ba 100644
--- a/packages/react-reconciler/src/ReactFiberCommitWork.new.js
+++ b/packages/react-reconciler/src/ReactFiberCommitWork.new.js
@@ -350,7 +350,6 @@ function commitBeforeMutationEffects_begin() {
     // Let's skip the whole loop if it's off.
     if (enableCreateEventHandleAPI) {
       // TODO: Should wrap this in flags check, too, as optimization
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
       const deletions = fiber.deletions;
       if (deletions !== null) {
         for (let i = 0; i < deletions.length; i++) {
@@ -360,10 +359,8 @@ function commitBeforeMutationEffects_begin() {
       }
     }
 
-    // $FlowFixMe[incompatible-use] found when upgrading Flow
     const child = fiber.child;
     if (
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
       (fiber.subtreeFlags & BeforeMutationMask) !== NoFlags &&
       child !== null
     ) {
diff --git a/packages/react-reconciler/src/ReactFiberCommitWork.old.js b/packages/react-reconciler/src/ReactFiberCommitWork.old.js
index 0fd77ff2dd1d4..4957356c30383 100644
--- a/packages/react-reconciler/src/ReactFiberCommitWork.old.js
+++ b/packages/react-reconciler/src/ReactFiberCommitWork.old.js
@@ -350,7 +350,6 @@ function commitBeforeMutationEffects_begin() {
     // Let's skip the whole loop if it's off.
     if (enableCreateEventHandleAPI) {
       // TODO: Should wrap this in flags check, too, as optimization
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
       const deletions = fiber.deletions;
       if (deletions !== null) {
         for (let i = 0; i < deletions.length; i++) {
@@ -360,10 +359,8 @@ function commitBeforeMutationEffects_begin() {
       }
     }
 
-    // $FlowFixMe[incompatible-use] found when upgrading Flow
     const child = fiber.child;
     if (
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
       (fiber.subtreeFlags & BeforeMutationMask) !== NoFlags &&
       child !== null
     ) {
diff --git a/packages/react-reconciler/src/ReactFiberCompleteWork.new.js b/packages/react-reconciler/src/ReactFiberCompleteWork.new.js
index b2bdbb0e0bca6..ef85cb32be9a2 100644
--- a/packages/react-reconciler/src/ReactFiberCompleteWork.new.js
+++ b/packages/react-reconciler/src/ReactFiberCompleteWork.new.js
@@ -357,7 +357,6 @@ if (supportsMutation) {
         node = node.child;
         continue;
       }
-      // $FlowFixMe This is correct but Flow is confused by the labeled break.
       node = (node: Fiber);
       if (node === workInProgress) {
         return;
@@ -425,7 +424,6 @@ if (supportsMutation) {
         node = node.child;
         continue;
       }
-      // $FlowFixMe This is correct but Flow is confused by the labeled break.
       node = (node: Fiber);
       if (node === workInProgress) {
         return;
diff --git a/packages/react-reconciler/src/ReactFiberCompleteWork.old.js b/packages/react-reconciler/src/ReactFiberCompleteWork.old.js
index e0d1dc4b66325..be5ff0d1ab3a8 100644
--- a/packages/react-reconciler/src/ReactFiberCompleteWork.old.js
+++ b/packages/react-reconciler/src/ReactFiberCompleteWork.old.js
@@ -357,7 +357,6 @@ if (supportsMutation) {
         node = node.child;
         continue;
       }
-      // $FlowFixMe This is correct but Flow is confused by the labeled break.
       node = (node: Fiber);
       if (node === workInProgress) {
         return;
@@ -425,7 +424,6 @@ if (supportsMutation) {
         node = node.child;
         continue;
       }
-      // $FlowFixMe This is correct but Flow is confused by the labeled break.
       node = (node: Fiber);
       if (node === workInProgress) {
         return;
diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js
index 7ed2249524d8b..f430a4cad6baf 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -771,7 +771,6 @@ if (enableUseMemoCacheHook) {
 function use<T>(usable: Usable<T>): T {
   if (usable !== null && typeof usable === 'object') {
     // $FlowFixMe[method-unbinding]
-    // $FlowFixMe[prop-missing]
     if (typeof usable.then === 'function') {
       // This is a thenable.
       const thenable: Thenable<T> = (usable: any);
diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js
index 559b96fb1a209..d5add2ffec5c4 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -771,7 +771,6 @@ if (enableUseMemoCacheHook) {
 function use<T>(usable: Usable<T>): T {
   if (usable !== null && typeof usable === 'object') {
     // $FlowFixMe[method-unbinding]
-    // $FlowFixMe[prop-missing]
     if (typeof usable.then === 'function') {
       // This is a thenable.
       const thenable: Thenable<T> = (usable: any);
diff --git a/packages/react-reconciler/src/ReactFiberHotReloading.new.js b/packages/react-reconciler/src/ReactFiberHotReloading.new.js
index 0b226a3de9a61..32ddb28afa365 100644
--- a/packages/react-reconciler/src/ReactFiberHotReloading.new.js
+++ b/packages/react-reconciler/src/ReactFiberHotReloading.new.js
@@ -51,7 +51,6 @@ import {
 import {enableFloat} from 'shared/ReactFeatureFlags';
 
 let resolveFamily: RefreshHandler | null = null;
-// $FlowFixMe Flow gets confused by a WeakSet feature check below.
 let failedBoundaries: WeakSet<Fiber> | null = null;
 
 export const setRefreshHandler = (handler: RefreshHandler | null): void => {
@@ -212,7 +211,6 @@ export function markFailedErrorBoundaryForHotReloading(fiber: Fiber) {
       return;
     }
     if (failedBoundaries === null) {
-      // $FlowFixMe Flow got confused by the feature check above.
       failedBoundaries = new WeakSet();
     }
     failedBoundaries.add(fiber);
diff --git a/packages/react-reconciler/src/ReactFiberHotReloading.old.js b/packages/react-reconciler/src/ReactFiberHotReloading.old.js
index 91d045a8944cb..0b553eaad3162 100644
--- a/packages/react-reconciler/src/ReactFiberHotReloading.old.js
+++ b/packages/react-reconciler/src/ReactFiberHotReloading.old.js
@@ -51,7 +51,6 @@ import {
 import {enableFloat} from 'shared/ReactFeatureFlags';
 
 let resolveFamily: RefreshHandler | null = null;
-// $FlowFixMe Flow gets confused by a WeakSet feature check below.
 let failedBoundaries: WeakSet<Fiber> | null = null;
 
 export const setRefreshHandler = (handler: RefreshHandler | null): void => {
@@ -212,7 +211,6 @@ export function markFailedErrorBoundaryForHotReloading(fiber: Fiber) {
       return;
     }
     if (failedBoundaries === null) {
-      // $FlowFixMe Flow got confused by the feature check above.
       failedBoundaries = new WeakSet();
     }
     failedBoundaries.add(fiber);
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
index 90591f8f0ba76..ff1f2d02364a1 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -415,8 +415,6 @@ export function addMarkerProgressCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerProgress === null) {
-      // $FlowFixMe[incompatible-use]
-      // $FlowFixMe[incompatible-type]
       currentPendingTransitionCallbacks.markerProgress = new Map();
     }
 
@@ -445,8 +443,6 @@ export function addMarkerIncompleteCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerIncomplete === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.markerIncomplete = new Map();
     }
 
@@ -474,8 +470,6 @@ export function addMarkerCompleteCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerComplete === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.markerComplete = new Map();
     }
 
@@ -503,8 +497,6 @@ export function addTransitionProgressCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.transitionProgress === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.transitionProgress = new Map();
     }
 
@@ -1680,8 +1672,7 @@ function prepareFreshStack(root: FiberRoot, lanes: Lanes): Fiber {
   if (workInProgress !== null) {
     let interruptedWork = workInProgressIsSuspended
       ? workInProgress
-      : // $FlowFixMe[incompatible-use] found when upgrading Flow
-        workInProgress.return;
+      : workInProgress.return;
     while (interruptedWork !== null) {
       const current = interruptedWork.alternate;
       unwindInterruptedWork(
@@ -3065,12 +3056,10 @@ export function attachPingListener(
       pingCache.set(wakeable, threadIDs);
     }
   }
-  // $FlowFixMe[incompatible-use] found when upgrading Flow
   if (!threadIDs.has(lanes)) {
     workInProgressRootDidAttachPingListener = true;
 
     // Memoize using the thread ID to prevent redundant listeners.
-    // $FlowFixMe[incompatible-use] found when upgrading Flow
     threadIDs.add(lanes);
     const ping = pingSuspendedRoot.bind(null, root, wakeable, lanes);
     if (enableUpdaterTracking) {
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
index 49b62e545e0bb..9f9c70ff2c0dd 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
@@ -415,8 +415,6 @@ export function addMarkerProgressCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerProgress === null) {
-      // $FlowFixMe[incompatible-use]
-      // $FlowFixMe[incompatible-type]
       currentPendingTransitionCallbacks.markerProgress = new Map();
     }
 
@@ -445,8 +443,6 @@ export function addMarkerIncompleteCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerIncomplete === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.markerIncomplete = new Map();
     }
 
@@ -474,8 +470,6 @@ export function addMarkerCompleteCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.markerComplete === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.markerComplete = new Map();
     }
 
@@ -503,8 +497,6 @@ export function addTransitionProgressCallbackToPendingTransition(
     }
 
     if (currentPendingTransitionCallbacks.transitionProgress === null) {
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
-      // $FlowFixMe[incompatible-type] found when upgrading Flow
       currentPendingTransitionCallbacks.transitionProgress = new Map();
     }
 
@@ -1680,8 +1672,7 @@ function prepareFreshStack(root: FiberRoot, lanes: Lanes): Fiber {
   if (workInProgress !== null) {
     let interruptedWork = workInProgressIsSuspended
       ? workInProgress
-      : // $FlowFixMe[incompatible-use] found when upgrading Flow
-        workInProgress.return;
+      : workInProgress.return;
     while (interruptedWork !== null) {
       const current = interruptedWork.alternate;
       unwindInterruptedWork(
@@ -3065,12 +3056,10 @@ export function attachPingListener(
       pingCache.set(wakeable, threadIDs);
     }
   }
-  // $FlowFixMe[incompatible-use] found when upgrading Flow
   if (!threadIDs.has(lanes)) {
     workInProgressRootDidAttachPingListener = true;
 
     // Memoize using the thread ID to prevent redundant listeners.
-    // $FlowFixMe[incompatible-use] found when upgrading Flow
     threadIDs.add(lanes);
     const ping = pingSuspendedRoot.bind(null, root, wakeable, lanes);
     if (enableUpdaterTracking) {
diff --git a/packages/react-refresh/src/ReactFreshRuntime.js b/packages/react-refresh/src/ReactFreshRuntime.js
index 2a971185f337a..1cce12585e48a 100644
--- a/packages/react-refresh/src/ReactFreshRuntime.js
+++ b/packages/react-refresh/src/ReactFreshRuntime.js
@@ -47,15 +47,16 @@ const PossiblyWeakMap = typeof WeakMap === 'function' ? WeakMap : Map;
 // We never remove these associations.
 // It's OK to reference families, but use WeakMap/Set for types.
 const allFamiliesByID: Map<string, Family> = new Map();
-const allFamiliesByType: // $FlowFixMe
-WeakMap<any, Family> | Map<any, Family> = new PossiblyWeakMap();
+const allFamiliesByType:
+  | WeakMap<any, Family>
+  | Map<any, Family> = new PossiblyWeakMap();
 const allSignaturesByType: // $FlowFixMe
 WeakMap<any, Signature> | Map<any, Signature> = new PossiblyWeakMap();
 // This WeakMap is read by React, so we only put families
 // that have actually been edited here. This keeps checks fast.
-// $FlowFixMe
-const updatedFamiliesByType: // $FlowFixMe
-WeakMap<any, Family> | Map<any, Family> = new PossiblyWeakMap();
+const updatedFamiliesByType:
+  | WeakMap<any, Family>
+  | Map<any, Family> = new PossiblyWeakMap();
 
 // This is cleared on every performReactRefresh() call.
 // It is an array of [Family, NextType] tuples.
@@ -74,8 +75,7 @@ const failedRoots: Set<FiberRoot> = new Set();
 // In environments that support WeakMap, we also remember the last element for every root.
 // It needs to be weak because we do this even for roots that failed to mount.
 // If there is no WeakMap, we won't attempt to do retrying.
-// $FlowFixMe
-const rootElements: WeakMap<any, ReactNodeList> | null = // $FlowFixMe
+const rootElements: WeakMap<any, ReactNodeList> | null =
   typeof WeakMap === 'function' ? new WeakMap() : null;
 
 let isPerformingRefresh = false;
diff --git a/packages/react-server-dom-webpack/src/ReactFlightWebpackNodeRegister.js b/packages/react-server-dom-webpack/src/ReactFlightWebpackNodeRegister.js
index 4c9b3447d028c..6ddfa87bc657e 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightWebpackNodeRegister.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightWebpackNodeRegister.js
@@ -9,7 +9,6 @@
 
 const url = require('url');
 
-// $FlowFixMe
 const Module = require('module');
 
 module.exports = function register() {
diff --git a/packages/react-server/src/ReactFizzHooks.js b/packages/react-server/src/ReactFizzHooks.js
index d87c3a6daebf5..8db3f319e3cc1 100644
--- a/packages/react-server/src/ReactFizzHooks.js
+++ b/packages/react-server/src/ReactFizzHooks.js
@@ -184,7 +184,6 @@ function createWorkInProgressHook(): Hook {
     if (workInProgressHook.next === null) {
       isReRender = false;
       // Append to the end of the list
-      // $FlowFixMe[incompatible-use] found when upgrading Flow
       workInProgressHook = workInProgressHook.next = createHook();
     } else {
       // There's already a work-in-progress. Reuse it.
@@ -529,7 +528,6 @@ function throwOnUseEventCall() {
 export function useEvent<Args, Return, F: (...Array<Args>) => Return>(
   callback: F,
 ): EventFunctionWrapper<Args, Return, F> {
-  // $FlowIgnore[incompatible-return] useEvent doesn't work in Fizz
   return throwOnUseEventCall;
 }
 
@@ -594,7 +592,6 @@ function useId(): string {
 function use<T>(usable: Usable<T>): T {
   if (usable !== null && typeof usable === 'object') {
     // $FlowFixMe[method-unbinding]
-    // $FlowFixMe[prop-missing]
     if (typeof usable.then === 'function') {
       // This is a thenable.
       const thenable: Thenable<T> = (usable: any);
diff --git a/packages/react-server/src/ReactFlightHooks.js b/packages/react-server/src/ReactFlightHooks.js
index fe485824c93a4..07de6602e6288 100644
--- a/packages/react-server/src/ReactFlightHooks.js
+++ b/packages/react-server/src/ReactFlightHooks.js
@@ -146,7 +146,6 @@ function useId(): string {
 function use<T>(usable: Usable<T>): T {
   if (usable !== null && typeof usable === 'object') {
     // $FlowFixMe[method-unbinding]
-    // $FlowFixMe[prop-missing]
     if (typeof usable.then === 'function') {
       // This is a thenable.
       const thenable: Thenable<T> = (usable: any);
diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
index 41ccc9867dd8a..02823183ea949 100644
--- a/packages/react-server/src/ReactFlightServer.js
+++ b/packages/react-server/src/ReactFlightServer.js
@@ -273,7 +273,6 @@ function attemptResolveElement(
             );
           }
         }
-        // $FlowFixMe issue discovered when updating Flow
         return [
           REACT_ELEMENT_TYPE,
           type,
@@ -768,7 +767,6 @@ export function resolveModelToJSON(
     // $FlowFixMe `description` might be undefined
     const name: string = value.description;
 
-    // $FlowFixMe `name` might be undefined
     if (Symbol.for(name) !== value) {
       throw new Error(
         'Only global symbols received from Symbol.for(...) can be passed to client components. ' +
@@ -898,7 +896,6 @@ function emitModuleChunk(
   id: number,
   moduleMetaData: ModuleMetaData,
 ): void {
-  // $FlowFixMe ModuleMetaData is not a ReactModel
   const processedChunk = processModuleChunk(request, id, moduleMetaData);
   request.completedModuleChunks.push(processedChunk);
 }
diff --git a/packages/react-server/src/ReactFlightServerConfigStream.js b/packages/react-server/src/ReactFlightServerConfigStream.js
index 7944137288eb5..8aa9e96d9ddf6 100644
--- a/packages/react-server/src/ReactFlightServerConfigStream.js
+++ b/packages/react-server/src/ReactFlightServerConfigStream.js
@@ -121,7 +121,6 @@ export function processModelChunk(
   id: number,
   model: ReactModel,
 ): Chunk {
-  // $FlowFixMe: `json` might be `undefined` when model is a symbol.
   const json: string = stringify(model, request.toJSON);
   const row = serializeRowHeader('J', id) + json + '\n';
   return stringToChunk(row);
@@ -142,7 +141,6 @@ export function processModuleChunk(
   id: number,
   moduleMetaData: ReactModel,
 ): Chunk {
-  // $FlowFixMe: `json` might be `undefined` when moduleMetaData is a symbol.
   const json: string = stringify(moduleMetaData);
   const row = serializeRowHeader('M', id) + json + '\n';
   return stringToChunk(row);
diff --git a/packages/react/src/ReactStartTransition.js b/packages/react/src/ReactStartTransition.js
index daafea7e9e67e..cf4359cf8d49f 100644
--- a/packages/react/src/ReactStartTransition.js
+++ b/packages/react/src/ReactStartTransition.js
@@ -20,7 +20,6 @@ export function startTransition(
   const currentTransition = ReactCurrentBatchConfig.transition;
 
   if (__DEV__) {
-    // $FlowFixMe[incompatible-use] found when upgrading Flow
     ReactCurrentBatchConfig.transition._updatedFibers = new Set();
   }
 
@@ -48,7 +47,6 @@ export function startTransition(
               'Otherwise concurrent mode guarantees are off the table.',
           );
         }
-        // $FlowFixMe[incompatible-use] found when upgrading Flow
         currentTransition._updatedFibers.clear();
       }
     }
diff --git a/packages/scheduler/src/forks/SchedulerMock.js b/packages/scheduler/src/forks/SchedulerMock.js
index ef1d03a9bd595..389edcb699e35 100644
--- a/packages/scheduler/src/forks/SchedulerMock.js
+++ b/packages/scheduler/src/forks/SchedulerMock.js
@@ -520,7 +520,6 @@ function unstable_flushNumberOfYields(count: number): void {
     try {
       let hasMoreWork = true;
       do {
-        // $FlowFixMe[not-a-function] found when upgrading Flow
         hasMoreWork = cb(true, currentMockTime);
       } while (hasMoreWork && !didStop);
       if (!hasMoreWork) {
@@ -546,7 +545,6 @@ function unstable_flushUntilNextPaint(): false {
     try {
       let hasMoreWork = true;
       do {
-        // $FlowFixMe[not-a-function] found when upgrading Flow
         hasMoreWork = cb(true, currentMockTime);
       } while (hasMoreWork && !didStop);
       if (!hasMoreWork) {
@@ -593,7 +591,6 @@ function unstable_flushAllWithoutAsserting(): boolean {
     try {
       let hasMoreWork = true;
       do {
-        // $FlowFixMe[not-a-function] found when upgrading Flow
         hasMoreWork = cb(true, currentMockTime);
       } while (hasMoreWork);
       if (!hasMoreWork) {