Emacs design question (was: run-mode-hooks)

[Kai Großjohann]

Richard Stallman <address@hidden> writes:

> I don't think we should insist that people use any particular
> construct for all major modes.  It would be useful to write
> a define-major-mode macro, but we should not decide to make
> all major modes use it now.

This example leads me to a question which is more general:

>From time to time I have found that you are opposed to introducing
(mandatory use of) additional abstraction levels.

In this case, you are suggesting that existing major modes continue
to do things "manually", rather than to use the new abstraction.
>From the past, I remember something similar about define-minor-mode
or define-derived-mode: there was a change to convert a mode to one
of them, and you reversed that change.  Obviously, you didn't want
the new abstraction to be used for all old cases.

I think that there is a lesson to be learned, but I fail to grok.

Can you (someone) enlighten me?

PS: Thanks for the lesson "eliminating duplication of code is not
    always desirable" that I learned some months ago when working on
    Tramp and discussing shell-quote-argument.

    Now I understand that developers' time spent on discussion is
    also a valuable resource that needs to be preserved.  When faced
    with the decision to rewrite some small amount of code such that
    there will be no problems at all, versus endless discussions of
    many developers about a small issue, one should just add the
    small piece of code and be done with it.
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