bug#50950: "(emacs) Mark" should contrast to "selecting" text in other editors

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Fri, 1 Oct 2021 21:31:22 +0200
> 
> Severity: wishlist
> 
> The section '(emacs) Mark' starts with saying:
> 
> "Many Emacs commands operate on an arbitrary contiguous part of the
> current buffer."
> 
> This makes it sound like this is an unusual, super advanced feature,
> when in the rest of the world this is just known as "selecting text".
> We should avoid the words "arbitrary" and "contiguous" which, while
> accurate, comes off as extremely highbrow for such an extremely basic
> feature.

I disagree that the region is a basic feature.  It may look
deceptively similar to text selections, but it isn't.  We have the
region, the active region, and the shift- and mouse-selected text,
which all look similar, and sometimes behave similarly, but they are
not identical.

> We should re-work this section to contrast the unusual parts of point,
> mark and region to the types of text selection that exists in other
> editors.  We can safely assume that the latter is well known.

The region and selected text are not identical.  The differences are
subtle and not easy to explain, but saying that they are the same is
worse than that, because it will trip users.

If anything, we should perhaps mention in this overview text that
Emacs has these 3 overlapping concepts (which are explained by the
sections of this chapter), because their addition to Emacs was
piecemeal and the overview was never updated to cover all of them.
But I don't think we should consider this a simple feature: that would
prevent us from explaining the subtleties that users should be aware
of.