While people always seem to "want to know why they were downvoted", a comment requirement would likely just encourage a low quality comment to receive more low quality responses. Especially since every person who potentially wanted to downvote something had to write a response to it.

(Imagine the opposite, if everyone who upvoted your comment had to reply "I agree" or something similarly useless.)

  >a comment requirement would likely just encourage a low quality comment to receive more low quality responses

  >Imagine the opposite, if everyone who upvoted your comment had to reply "I agree" or something similarly useless.)

I suppose it could be done Slashdot style where [AFAIK. I've not been on there for years] you don't have to write a reason for an up- or downvote. You just select from a series of icons representing; "insightful", "funny"... etc.

A system like that wouldn't add much overhead to voting on a submission, but would give an indication as to why the voting had gone that way.

I think that's a good idea. Adding an extra step would give people pause before downvoting and perhaps make them think about the OPs perspective for a second.

In theory it should reduce the number of knee-jerk reactionary downvotes.