I don't know if this is a new trick, but I have found a way to squeeze some extra reputation on old answers.
Say there is a question by another user with many answers where an answer of mine has gained a lot of attention (comments, votes). Every time I add a new answer to that question, the questions is regurgitated to the top of the active questions stream. Apparently this causes it to gain renewed attention and it squeezes out of my answer some extra reputation drops.
It is tempting to do it specially if the answer is near a "badge threshold".
It works best when the answer represents a rather polemical point of view, or there is a kind of discussion going on between the answers, and not when there is just an attempt to find an answer to a technical issue.
I don't know if this is a bug and how can it be fixed or if it should be fixed at all.