Case in point ...

I've occasionally found a comment that I felt was both mean-spirited and largely content-free. I've down-voted that.

Then I wondered if that person had a history of such comments, so I've brought up their profile, looked through their comments, and attempted to assess each one on its merits. In cases of doubt I've left them alone, but if I've felt that the comment in question was again mean-spirited and content-free, I've down-voted that as well.

I've realised that such actions, while intended well, might be viewed as "punishing" the "contributor" in question. Further, I suspect that PG already detects and inhibits this behavior.

So here we have a case where I believe I'm doing the right thing to help reduce the mean-spiritedness of comments, and I get prevented from doing so.