RE: Eliminating "changed in Emacs outside of Customize"

[Drew Adams]

    If I remember correctly, ...autoloaded defcustoms...

Whew! What a lot of information. I hope this is documented somewhere, so
that others can be privy to it too. Thank you.

    this feature is scheduled for elimination,
    because it creates incompatibility between different Emacs versions.

That's the first time I've seen reference to such a backward-compatibility
concern - and I'm glad to see it. I don't say the concern has never been
there, but this is the first time _I've_ seen a hint of it. (At least as far
as Lisp is concerned - I admit that I've seen concern about legacy user
interaction.) Whenever I voice such concern I usually get replies like "just
update to the latest".

Unless of course you didn't mean different versions in the sense of 19, 20,
21, but in some other sense (Windows vs GNU/Linux; Chinese vs Arabic;
graphic vs text-only; color vs B&W; metric vs English; ...).