Fundamental mode.

[Lute Kamstra]

Modes derived from fundamental mode run after-change-major-mode-hook
twice because fundamental mode runs it unconditionally.  Fundamental
mode should only run after-change-major-mode-hook if delay-mode-hooks
is nil.  We can either test this directly or use (run-mode-hooks
'fundamental-mode-hook).  The latter also introduces
fundamental-mode-hook, of course.  I see no problem with that, but I'm
a bit surprised it hasn't been done already.  (So I suspect there is
some reason for not running fundamental-mode-hook.)

What do others think is best?

Lute.