The biggest peeve is sometimes I vote up an answer mid-way through reading it, and the "don't forget to accept" message blocks the remaining text, so I scramble and triple-click it until it closes.
Anyways I frequently scan my question list and search for SO's reminders, ("Consider accepting an answer") so the "don't forget to accept" is wholly unnecessary to some, and there should be a way to disable it. Do you think so too?