> No, the point of the proposal is to allow you to make further changes in
> response to user feedback. I assume you can't add things anymore once
> the ABI is declared "stable". Can you?

Adding things would be possible, although undesirable. Extension modules
built against the initial release would continue to work
in the new release; extension modules built against the new release
would work with the old release as long as they don't use the additions.
So I'd be in favor of extending the ABI conservatively, as long as
developers explicitly need to opt-in to use such additions (e.g. by
defining a macro)

Most of the recent ABI changes would have fallen under such a policy;
the only incompatible change is the removal of a field (issue11135).
If that isn't carried out before 3.2 is released, then the field
would just remain unused.