For me it's bad grammar, repetitive themes, putting down the other person, whom we can't hear from of course...
Most Helpful Girl
Ignoring content, A closed mind that's really only looking for one specific answer, like a question trying to rally up a pity party, or, like you said, someone who puts down answers he doesn't agree with. Why put down someone who went through the trouble of trying to answer your question? I flinch at bad grammar, but usually it doesn't matter unless it's coupled with a really ignorant person. And then there are the people who ask an alright question, but are subconsciously looking for an answer that makes them feel better, so they start commenting answers trying to "make their question more clear" because, obviously, the answerer wouldn't feel that way if they "read the question right."