I write in third person, and past tense.
I used to write in third person, PRESENT tense, but changed my style when I went from one MuD to another, and found that past tense works better. It also depends on your community. The new community I'm in writes more in past tense than in present tense, and even though not everyone writes in the same tenses, it all still works out.
If I was writing by myself, I might write in first person from the perspective of the character I'm 'animating', but if there are others around and they want to read or interact with my post, then there's the added problem of them feeling a bit put off by reading someone's 'first person' perspective as if it was their own character doing those actions, because they're reading 'me, I," instead of 'he/her'. Does that make sense? >>