bug#23798: 25.0.90; Underscore for emphasis in Info?

[Drew Adams <drew.adams@oracle.com>]

> > Is there any other kind of emphasis that is used?
> 
> Yes, there's @strong, rendered as *foo*.

I see.  I suspected that, so I searched for it (in the Emacs and
Elisp manuals).  I did not find any matches that would seem to
reflect that.

And I did find _lots_ of matches that instead mean something
else, such as a buffer name: *Messages* (with and without
enclosing single quotes - with quotes is not problematic).

So I don't think it is very feasible to try to render *...*
using, say, ... with a face `info-strong' (e.g. bold by default).
I think trying to do that would be too problematic.

It is unfortunate that Info "renders" what is clear markup, e.g.
@strong, by something that is not markup and not clearly
notational, and so is easily confused with ordinary text.  If
@strong were "rendered" as, say, **...**, the risk of confusion
would be greatly reduced.  (Is something like that a possibility,
or is this "rendering" a given?)

As it stands now, the case for fixing _..._ for single words is
reasonable, I think, but I don't think that's the case for *...*.

Maybe you have a better suggestion?

If you decide to do nothing wrt this enhancement request, perhaps
you would at least consider to have the Info help, for Info that
is displayed by Emacs, include a "notation" section that tells
users that "_..._" is emphasis and "*...*" is strong emphasis.
We already have node (info) `Help-Inv', which is along the same
lines, but the notation is not described anywhere, AFAICT. 

Whether or not we add a section for notation in general, if we
apply a patch such as I proposed, it might help to also point out
in `Help-Inv' that turning on `visible-mode' shows the underscores
that actually surround emphasized text.  IOW, `M-x visible-mode'
to turn it on shows emphasized text in `Help-Inv' as "_always_"
and "_default_" (with the words emphasized using face `italic' by
default).

The main problem this report points to is that these notational
things are not introduced/mentioned anywhere.  There should be
some place where the Info notation is introduced.  (Yes, few
readers will ever come across such a notation description, but it
would still be better to have it than not to have it, IMO.)

BTW, I see that (info) `Help-]' includes "_at the same level_"
and "_regardless of level_": multiple emphasized words.  These
phrases would not be fontified using the patch I included, which
acts only on single words.

On the other hand, since `visible-mode' can be used to show
hidden `_', maybe it would be OK to use a regexp that highlights
words possibly separated by whitespace?  IOW, it is very easy
to compensate for improper hiding of `_', just by turning on
`visible-mode'.

But (a) most users won't know about `visible-mode' and (b) more
importantly, they won't know whether something is hidden or not,
except by noticing that some text has been emphasized (which is
not super obvious with face `italic').  I fear that most users
would be misled by this.