I've stopped commenting on posts that really aren't looking for info. I'm pretty bored with snarking jerks/people fishing. If someone is genuinely confused, that's completely different. It seems like there are so few genuine questions lately.
Oh and it annoys me when 10,000 people respond with the same suggestion/response. I will quote someone if I agree and want to add something else, but if 20 people have said the exact same thing as I would... I don't like to repeat it.
ETA The last part obviously isn't valid for giving congrats over something or sympathy for a loss. Then I have no issue with people repeating.