A few things, really.
First, I -really- hate it when people assume that Lore-following means cookie cutter "my way or ur doin' it rong". You can have unique characters that follow the Lore without it all being standardized, boring, predictable crap. So, in short, elitists that think there is only one way to do things or it's wrong, despite the fact the Lore may support other options/angles/whatever.
Tauren that refer to their hands as paws. :| No. They're hands. See those thumbs and separate, non-padded digits? Even if they were not hands, you are an ungulate, meaning you wouldn't have paws anyway. I honestly think this is more a furry-fandom thing leaking through to some Tauren RPers than anything else, but it grates on my nerves.
Pseudo-RPers that are just out there for the be-all-end-all of ERP. AKA cyber-sexings thinly disguised as RP. No, I've no overall problem with ERP; I've done it in the past but found it's just not that interesting to me, personally, nor am I interested in the amount of OOC drama that usually comes with it. But if you want to do it for character development and real story purposes, go for it - s'fine. But don't just make a character for the sole purpose of getting some text-nookie and then pretend you're an RPer. You're cybering, plain and simple.
Night Elves that act like tall, purple humans. Ok, I can see some of the young nelfs being a bit rebellious against the "old ways", but the majority of nelfs are not supposed to be especially young, nor especially kind, nurturing and silky. This race spent thousands of years in semi-seclusion, living very close to nature, fighting trolls and the like. Culturally, they are fairly savage, feral and not too trusting of outsiders. Their style of "sophistication" is not quite peaceful and lovely and kind, which I see being RP'ed out a lot. It's going to take more than a few short years to change the outlook of the "typical" hundreds-of-years-old night elf in this regard.