Hmm, let's see...

# Overly flowery and extensive premises and introductions! Whatever there is to be said about what your roleplay is should be said concisely.
# People who take too much pride in their successful roleplays!—"I did this and I did that. I have fifteen successful roleplays running. Look at me, I know stuff!"
# Those who are overly sensitive to critique, constructive criticism, whatever you want to call it! If you're not willing to change or improve, then what's the point?