My big peeve when RPing with anyone is when they act super self-important. Like the whole damn RP revolves around them, and that everyone should bend forward to their wishes just because! When most of the time, the RP will totally go just fine without them. It's a surefire way to get me to hate you - and want you far away from my RP as possible - in three posts or less!

Another thing that's starting to get to me is whenever someone complains about long posts/character sheets... in the [i]Advance[/i] Section. Okay, I get it, some people don't like them (Or that it might be a bit of an inconvenience to read them), but there's two sides to that coin. I do like reading a long, meaningful, and well written, post than something shat out in five minutes. It should more of a sign of dedication and passion that you're willing to write such a long post. And, this might sound contradictory, but it's sometimes a [i]real[/i] chore to write a post sometimes. Last thing I want to hear is someone whining about the length of the post, rather than the content - but whatever.

But here's the simple solution, don't like long posts/sheets? 

[i]Then get out of the Advance section, you moron.[/i]

Last complaint is a little bit less specific, and something I wanted to share since I find it humorous. There was this one chick who joined an RP I ran a few months ago, but she kept up this annoying image that "nice characters" are better. She complained about how she disliked the "mean" characters (A huge chunk of mine were these characters lol), or whatever. And basically blowing herself about how her character was the nicest and purest special snowflake out of all of them! And I'm sitting here like - Bitch, do you want everything to become a boring hunky dory circle-jerk where everyone does nothing but bake pies for the poor and homeless. I mean, I don't particularly wank "mean" characters either, but I like giving my characters actual flaws (And on the flipside, positive traits so they're not edgy 90's anti-heroes), and things to work around. Makes them feel a bit more human, imo. I find it really hard to root for a character that's already perfect, and has no room to develop. The characters she disliked (And some of the nicer characters for that matter) had way more depth and personality than her own character would ever had. 

Then again, her character was basically a self-insert, so the self-wanking wasn't all that unexpected.