It seems that Xcode supports Unicode.

Inserting an Unicode character the alert dialog says: "You are trying to 
insert characters that cannot be handled by the file's current 
encoding.  Do you want to promote the file to a richer encoding?" 
<Promote ro UTF8> <Cancel> <Promote to Unicode>

I can't see that as a priority for the Editor. And it seems a difficult 
task.

Michele.