Re: highlighting non-ASCII characters

[Juri Linkov]

> What I'm saying is that there are two issues: non-ASCII chars in general
> (which I personally don't want to display in any special manner:
> they're just as normal as ASCII chars), and then there are "chars that
> are out of place or that may not be what they look like", such as the
> weird "K" in the other message's "OK" (which to me, is similar to the
> NBSP char in that it is meant to be displayed in the same way as some
> other char, so we want to call the attention of the user to the
> difference).

There is another case where non-highlighted out of place chars
cause problems: http://thread.gmane.org/gmane.emacs.devel/121494

When I look at NBSP chars in cc-engine.el, I see them as `EQUALS SIGN'
(actually `C-u C-x =' says they are `BOX DRAWINGS DOUBLE HORIZONTAL').
That's because of the wrong coding used (there is no coding: tag,
so they are displayed with my default koi8).  When Miles reported this
problem with NBSP chars in cc-engine.el, I found nothing suspicious
because equals-sign chars don't look out of place.  And only when
I grepped for non-ASCII chars, I discovered them.

What should be a heuristics to highlight these problematic chars
that look like normal chars?

-- 
Juri Linkov
http://www.jurta.org/emacs/