Yeah, this has been requested before.
I am particularly aware of it right now because I've been watching my 30-days karma drop slowly and steadily for the last couple of days, but I have no idea what in particular people want less of.
That said, I suspect that's just because I'm getting individual downvotes across a wide set of comments in the 0+/-2 range, and changing the way that information is displayed won't really help me answer that question any better than the current system does.
have you been making less comments? My 30 day karma depends far more on the amount of commenting I've been doing than on anything else.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.