I have done first person that actually didn't feel like cybering, which was quite a surprise to me. But the biggest barrier is that that was a good case, most of the other cases of first-person that I've done are pretty blatantly trying to get off. So, it's not a blanket ban on first-person but I definitely feel as though it takes a skilled writer to separate themselves from the character. Third-person, past tense, is generally where my RPs lie simply because it's standard in fiction writing. It's hardly THE standard, of course, considering first-person novels are far from unheard of. It's also just easier when you're juggling more than one character because first-person makes no sense in that regard.