When I play Draven, I tend to get a bit...in character...if I'm doing well.
Typing "Man I'm good" or "This is where Draven shines" after a kill, "Perfection? I got that" after a multikill, etc.

On the one hand, I'd consider this horribly rude if I were playing any other champ.

On the other hand. I'm playing Draven. It's in the nature of the champion.

Not as acceptable as roleplaying Mundo.

More acceptable than most.

Do you say "Too easy" after winning as well? That is where I draw the line.

If you're not roleplaying as Draven while Draven, you're not doing it right.

You gotta Draven to truly Draven the Draven and therefore, Draven.

When I play Draven I feel compelled to roleplay. xD

Whenever I play draven I just say "DRAAAAAAAAAAVEN" at the beginning of the game... people on both teams kind of just role play off of that. "Guess it really is your league, Draven." and also "Looks like it's your time to shine, I suppose"

All the hues.

I don't feel right if I'm not roleplaying him

I do that sort of thing too and I love it, but eventually it'll get you banned. Almost anything out of the ordinary will get you banned if you do it enough.