I wouldn't do it either. Micarta uses thermosetting resins to harden, I'd think that even if you managed to burn a handle in without asphyxiating yourself, the material could be significantly weakened.
I have heard of using lower heats on the tang, like 3-400 degrees, to "iron" the fit in just perfect after previous shaping, when fitting up scales onto integrals and such, mostly with wood but I think also with micarta- but I don't see a need for it personally.