I don't give out too many reviews on people but if a person is acting out unnecessarily, I'll give them a negative review.
A few months ago I did give out quite a few, because there was a long string of people that I encountered on Halo Reach that weren't doing just the quick teabag after killing like many jerk players do. But they were sitting there for several seconds doing it, while hitting my body and shooting it as well. They did it so long at times I could re-spawn and run up and assassinate them.
In a two day period I reported around 8 people as unsporting for doing it, then I didn't encounter people like that ever again.
I hate the whole being a jerk teabaging thing that has become a part of gaming. Just play the game and move on. Besides it tends to be people that aren't even that good that do it. I played against one team that ever one of them did it and they lost 50 to 15. Maybe if they weren't so busy teabaging the could actually play the game and get better.
Edit: Also, what I find hilarious is that a few of the people I ended up giving unsporting reviews for such conduct, they end up messaging me things like, "Let's go 1 on 1 punk", then they send that "So and so" wants to play Halo Reach, message.