Unicode characters in mathed

[Jean-Marc Lasgouttes]

Hello,

A relative has been using LyX recently, and it is interesting to see how 
the use is different from what I would do.

In particular, instead of typing \neq in mathed, why not copy and paste 
a ≠ from some PDF or HTML page?

When doing this, two things happen :
1/ on screen, there is no spacing around the ≠
2/ in LaTeX output, the character is exported as \neq and all is well

So how should I solve problem 1/ ? I see 3 solutions
a/ replace ≠ with a \neq directly in the document at input time; we 
might not want to do that in case we eventually use unicode in math too
b/ replace ≠ with a \neq on screen only
c/ keep the ≠ on screen, but use the mathrel math class from \neq so 
that we have a good spacing

Then, I see that there are two ways of matching \neq to U+2260:
i/ lib/unicodesymbol has a "mathcommand" entry for that (which is 
presumably used right now)
ii/ lib/symbols also links these elements

Which one is more reliable for what I want to do?

My general problem is that, while I see what happens with \neq, I 
suspect that many weird things can happen with other characters.

Any advice?

JMarc