Ahahahaha. That a program knows how to do Unicode doesn't mean it has to *force* Unicode. The ó of Revolución fit fine in Latin-1.This doesn't: 人. Or one doesn't need to go Chinese, just Greek: αδγ.
Now, my question is why Mail.app felt the need to change the font of the text that followed 人, but not that before it. It's certainly not that what the body of the message told it to do.
Darrell
