PEP 678: Clarify how the notes tuple is updated and when it is copied

pep-0678.rst

@@ -140,10 +140,10 @@ are collecting multiple exception objects to handle together. [1]_
 Specification
 =============
 
-``BaseException`` gains a new read-only attribute ``__notes__``, an initially
-empty tuple, and a new method ``.add_note(note: str)``.  ``note`` is added to
-the exception's notes, which appear in the standard traceback after the
-exception string. A ``TypeError`` is raised if ``note`` is not a string.
+``BaseException`` gains a new new method ``.add_note(note: str)``. Notes are
+exposed as a tuple via the read-only attribute ``__notes__``, which is backed
+by an internal list, and appear in the standard traceback after the exception
+string.  ``.add_note()`` raises ``TypeError`` if ``note`` is not a string.
 
 ``del err.__notes__`` clears the contents of the ``__notes__`` attribute,
 leaving it an empty tuple as if ``.add_note()`` had never been called.  This
@@ -319,8 +319,8 @@ proposed ``__notes__`` semantics, but this would be rarely and inconsistently
 applicable.
 
 
-Store notes in ``ExceptionGroup``\ s
-------------------------------------
+Store notes in ``ExceptionGroup``\ s, but not other ``Exception``\ s
+--------------------------------------------------------------------
 Initial discussions proposed making a more focussed change by thinking about
 how to associate messages with the nested exceptions in ``ExceptionGroup`` s,
 such as a list of notes or mapping of exceptions to notes.  However, this would