bug#57250: emacs-lisp-mode not highlighting single characters `k' in comments

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

> > But if the character sequence within tick ` and a single quote ' is a
> single
> > character, the character does not get highlighted.
> >
> > Example:
> >
> > ;; Insert `k' for words with initial values.
> >
> > The character k does not get highlighted.
> 
> That's because k here is more likely to be a key than a Lisp symbol.
> 
> So I think this is expected.

FWIW, I don't think it should be expected.

And even if it were expected to consider it
a key, that's not a reason not to highlight
it.  Keys such as `M-x' do get highlighted.

To me, this is a minor bug or a nice-to-have.
If it can be fixed reasonably then that would
be good.

We need not expect, for this bug fix, that
things like `C-x C-x', which contains a SPC
char, would also get fixed (highlighted).

That would be nice, but there's only so much
that reasonably can be done.  Highlighting
everything from ` to ' would likely introduce
a fair number of problems.  (And then there
are things like a `C-x C-x' that's split
across a newline...)