You know what I hate. Not just in RPs but in all online conversation on the web, but this extend to RP still. It's the wait for people to reply, no not reply to your post I mean they replied but you still got to read it. That wait. Especially when you see that BIG 1 on your alert for a forum or thread and as soon as you see it it's like opening an envelope but there's no details on front. 

In real life I can pick up a letter and deduce if it's taxes or something bad but on the internet in general it's like you get a bunch of mystery packages and you secretly hope that one of them isn't a crazy ex threatening you in slurs with her own menstrual blood. It's the same in a forum or RP, you get a notification from a GM or something and immediately the theme from count down starts ticking in your head as you go "Oh shit. I've been kicked for accidentally offending someone or coming off as disingenuous haven't I" or some guy dive rolls out of the blue to argue with your use of binary sex labels or some crap.