I feel like I have a scenario like this, but recently I gave an answer which received a down-vote, as did one other answer to the same question, and then mine got a second down-vote, yet there were no comments explaining the down-vote.
What made the answer "not useful"?
Was it because I saw the score change and thus didn't report what Roland did ("When I play the quiz, my total score always stays at 0, so there must be something wrong.")
was it because the review wasn't very comprehensive?
were the suggestions considered bad practice?
was it because the suggestions were not accompanied by example code?
Perhaps I am just over-reacting about these down-votes, but it is quite frustrating to not have any constructive feedback. I have been told "Code Review is a participation thing, you should not have to worry about people downvoting you for nothing"1 but not only does it take away rep, it also has adverse affects on progress towards badges like tag-specific badges, the illuminator, etc....