Re: lax matching is not a great default behavior

[Eli Zaretskii <eliz@gnu.org>]

> From: Andreas Röhler <andreas.roehler@online.de>
> Date: Tue, 1 Dec 2015 10:23:09 +0100
> Cc: John Wiegley <jwiegley@gmail.com>, Andreas Schwab <schwab@linux-m68k.org>,
> 	Drew Adams <drew.adams@oracle.com>
> 
> Notion resp. implementation of case-folding is unclear outside ASCII and related.

What is "related" to ASCII?  Do you mean Latin characters?  If so, the
notion of case-folding is clearly well beyond these: Cyrillic and
Greek characters are 2 obvious examples.

Moreover, the Unicode Character Database has other scripts that have
"small" and "capital" variants of letters: Armenian, Georgian, Coptic,
and a few old scripts.  Also, many symbols have small and capital
variants.  IOW, this attribute is in no way limited to ASCII and Latin
scripts.

Scripts that don't support case variants are not affected by
case-folding at all in Emacs.

> There must not be anything to be folded in a buffer. Folding is a notion which makes sense in special cases only - which are common in ASCII world, but not a reason for a default.

As mentioned before, this is contrary to a long-standing tradition in
Emacs: searches are case-insensitive by default, and not only for
ASCII characters.  Emacs is primarily a programmer's editor, and most
programming languages use ASCII characters for program source.  So by
your own logic above, case-folding should make a lot of sense in many
Emacs buffers.

> New users should not be bothered with this vast area.

I don't think they are bothered.  The defaults work seamlessly, no
bother is expected or required.

> GNU Linux is case-sensitive and Emacs should start by default like that.

I don't think the fact that Linux filesystems are case-sensitive is
relevant to searching buffer text for strings.  They are two entirely
unrelated features.