I've been using the Review feature in SO to read-through new users's posts and provide feedback. I rarely downvote a mal-formed question. Instead, I generally leave a helpful comment w/ some suggestions. There are times when I leave a comment, but somebody else downvotes, so it looks like I was the one that downvoted. Because of this, I feel like some users seek revenge by finding answers/questions from me and downvoting.
Now, that's nothing new, and I know others have suggested we be allowed to leave anonymous comments. That's not what I'm asking. Instead, is it possible to prohibit someone from downvoting another user twice in the same day? I feel it's highly unlikely that userA is going to stumble upon multiple separate questions/answers from userB in the same day, much less likely that userA will find all of userB's material worthy of downvotes in the same day.
The only recent example I have of this is that two of my questions were downvoted at the same time earlier this morning. These are questions that have been received well by other SO users, and have never been downvoted. Each question has a handful of positive votes and, in the latter example, even a few stars. I realize it's possible that someone could take issue w/ each of these questions, but I find it unlikely that two different people downvoted these two generally-well-liked questions at the same time. I'm guessing it's the same user blindly-downvoting.