Is it okay to use another player's character 'fantasia' as your own without asking?

[Rongway]

As long as you don't pretend to be the other person, and you don't do it to mock/harass the other person, it's "fine". It's a little lame and unoriginal but not "wrong" in any moral sense.

However, misrepresenting yourself to pose as someone else and harassment are both offenses covered by the rules.

[Rokke]

I think some looks will end up pretty similar inherently as our character creation is so limited, especially if you use one of the "popular faces", but willfully making an exact copy of someone else is kinda weird.