I like that, at least then the person receiving the negative feedback has something to go on instead of having to guess as to the reason for the down-vote. The given reason itself can then become a discussion point. For instance if someone was down-voting a comment because they felt that the theory expressed in the comment cannot possibly work, then when they say that is the case they can be called to explain their position and provide evidence for it, or have their objection refuted. That way everyone can learn from the process.