I have seen the pattern many times and it always gives me a sad face. It goes like
- Peter puts up an answer
- Anonymous downvotes Peter's answer, without commenting
- Peter asks "@downvoter, can you please comment?"
If Anonymous comments and gives reason for his downvote, everyone knows he downvoted. Since downvotes have (unfortunately) some sort of negative emotion attached, Anonymous fears for his reputation within the community.
I think that the major reason people not comment on downvotes is because they will be known as "The downvoter". We can rid of this problem by showing the name of the downvoters. Being known already as the downvoter, the downvoter is much more likely and from what I can see even wants to give reason of why he downvoted.
Everyone is pleased to know the reason of a downvote, so this will do everyone a favor. But there might still be some people who are too afraid of this. In such a case, I think those people should pay the absence of their name being shown with reputation points. For people that make their name known as one of the downvoters, I think we should not or should take significantly less rep from them. So Anonymous has two alternatives:
- Anonymous decides to downvote and to make his name public
- He won't pay any rep, and will be urged to explain his comment
- Peter will be pleased to know why he was downvoted.
- Anonymous decides to downvote and not make his name public
- He will pay a downvote fee (-2, -5 ?).
- Peter won't be pleased, but Anonymous had to pay price for this.