For terminology: a 'pet peeve' is something that you find irritating, but it's below the threshold of reactive annoyance. Or to put the question in a more positive light: What's the one single thing you would change at TSE?
One 'pet peeve' per answer.
Please give multiple answers if you have more than one 'pet peeve'. We really need to see what centrality exists. If people learn that they share a common sentiment, then it can lead to brainstorming and similar positive results.
For example, my 'pet peeve' is about OP's that ask a useful question and then never return. I know there's nothing to be done about it, but that's my 'pet peeve'. As another example, I have a 'pet peeve' that OP's are horrible at tagging, sometimes you think that they just select a tag because the system requires it. These examples would be TWO answers.
So having explained it, what's your 'pet peeve' at TSE? It's local to us and not about SO in general. But TSE includes chat and META in addition to the Q/A site. And don't be bashful, you might find people agree with you!