A relatively new-comer that had been given a few weeks sabbatical for many egregious answers has returned. I suspect he was (and still is) the culprit behind the 'carpet-bombing' of down votes left to every person where his answer was down voted. A spiteful vengeful, "I don't know who did it so I will down vote everyone who answered"-type of mentality. I'm sure it's this individual because before his vacation my answer's always received 1 down vote if we both answered the same question. During his hiatus? No down votes. Since his return? I'm receiving down votes again. Yeah, I'm not perfect. My instructions are fallible. Sort of suspicious that down votes fly, fast and furious when this guy shows up. How is this behavior prevented or stopped? Or is it condoned by the upper echelon?
If his votes are targeted against individual users then it's highly likely that they will be automatically reversed by the system. If this isn't happening (because the votes are just against those who happen to answer the same questions) or continues after a reversal, flag one of their posts with a custom flag and we'll look into it.
We can ask a community manager for a vote invalidation, suspend the user or even remove their account if the situation warrants it.
My understanding is that moderators have limited ability to control serial downvoting. The system has a built-in mechanism to identify serial downvotes and it seems moderators simply defer to the automated system. Personally I think moderators should be more proactive in reversing serial downvotes, but at the end of the day, it is sort of a moderator problem that we can do nothing about.
I would suggest not getting too wound up about some guys bad answers. Its not your job to be the answer police and so what if some bozo is posting bad, hostile answers? Don't read his posts if you don't like them. Trying to censor stuff just hides the problem, it does not make things better.