Right now, mIRC does not yet support Unicode (although Khaled has apparently said he plans to add support someday). But for those who were worried this would change the default mirc font (as I read in an old thread), I'd like to share what I've been working on for the last few months, a Unicode version of Fixedsys:

http://www.fixedsys.org/

The download also includes the a version of Fixedsys that is not Unicode but does contain some of the missing Extended ASCII characters in Fixedsys, which is more useful until Unicode support does show up.

-Darien