Now one thing I hate is the fact that some people RP in first-person, as well as those who writes in present while EVERYONE else writes in past tense. 

It's taking it to a whole new level of idiocy once you write in present, past and a whole lot of other times in the same post! I mean, make up your mind! Did your character do it, is he doing it now or is he simply contemplating taking that action. I can't fricking tell because you're writing all over the god damn space-time-continium!