Re: "Emacs 21"

[Richard Stallman]

    Are you sure?  This is the Lisp introduction, and for version 21 included
    all these discussions.  Certainly 20 is less relevant once 22 is out, and
    19 even less so, but do you really mean to remove all of it?  (I am not
    arguing either way on the matter, just describing past practice.)

For a beginner learning Lisp on Emacs 22, talking about old Emacs
versions is a digression.  Digressions interfere with communication.
Unless there is some special important reason I can't envision,
it is better to eliminate everything about old versions.

    > The latter, we should update (if necessary) so that they handle Emacs
    > 22 properly.

    By "properly", do you mean "recognize as distinct from all prior (and
    perhaps subsequent) Emacs versions, or do you merely mean that they should
    not produce literally false output (e.g., diagnosing Emacs 22 as 20)?

Each of these examples serves an educational purpose.
So each should be updated so as to serve its purpose well
in a world where Emacs 22 is being used.