ZeroWidthString component why is \uFEFF sometimes rendered and sometimes not

[bmingles]

In the ZeroWidthString component, there is a conditionally rendered \uFEFF character:

{!(IS_ANDROID || IS_IOS) || !isLineBreak ? '\uFEFF' : null}

https://github.com/ianstormtaylor/slate/blob/main/packages/slate-react/src/components/string.tsx#L132

I'd like to better understand why / when it is needed vs not.

[pex]

Same, especially since it leads to hydration errors on mobile devices in SSR scenarios.

[bmingles]

Related issue #5760