I tend to avoid fandom or fanfic role plays, whatever you want to call them. I want to explore new territories, not tread old ground. I'm not bashing people who want to role play in the Harry Potter world or in the DC Universe. You do you. It's just not for me. I would rather role play in an original setting even if it is obviously inspired by something already out there. I don't want to role play in Hogwarts or Gotham City but I'll role play in a magical school setting or a world full of superheroes.
I have more role playing pet peeves but most of them have already been said so I'll end with this. I can't stand it when someone is too picky or has an elitist attitude. Personally, I'm willing to role play in a setting or a plot that might otherwise bore me if it were in a novel but I can respect that some people want to maintain certain standards. I would certainly like to role play with the highest quality writers possible but I'm not going to snub somebody just because I don't think their writing is "up to par".
Besides, I probably have an overestimation concerning my own skills and there very well may be a better writer out there role playing with me who otherwise wouldn't if they held to certain standards. I think the best way to become a better roleplayer/writer is to, put it bluntly, do so with people who are better than you but you can't do that if they all snub you.
On the other side of that coin, I also don't like it when people are shamed for wanting to role play with a writer of a certain skill level. If you have a particular story in mind that you've been working really hard on and you want to invite certain people whom you know are excellent role players, you shouldn't be made to feel guilty for not wanting Joe Schmo to join because his writing just isn't quite up there. Any long-term member of a role play site is going to have more than one game under their belt (often times more than one at a time) and I think that as long as they are not excluding Joe in everything that they do, then they should be allowed to indulge in some "higher caliber writing" in that special story they've been working on.
That last one is hard to talk about because I don't want to come across as sounding like a snob. Trust me, I don't think that I'm the best writer in the world or anything. I've read a few posts from different role plays here on STC and let me tell you, I'm not even the best writer on this site. If I ask to join a role play and I get turned down, even if it is because they don't think my quality is quite up there, then as long as they don't tell me, "You suck, go away" then I can take my rejection with dignity and resolve myself to keep writing, getting better, and having fun.