Some basic info on serial voting: math.meta.stackexchange.com/tags/serial-voting/info and What is serial voting and how does it affect me?

@T.Amdeberhan There are some scripts which detect (and revert) serial voting.

The only related post on meta.MO I found is this: What does “serial upvoting reversed” mean?

@ToddTrimble Since you are a moderator perhaps you will have something to say on the above question...?

Would it be reasonable to make a post on meta asking about possibilities to revert serial voting and revenge downvotes. (Maybe there already is such a post and I simply did not find it.)

@T.Amdeberhan Perhaps this post on meta.MO might also be of interest for you: VIndictive downvoting--what can be done about such childishness, errh, lack of professionalism?

The above post has answers by Todd Trimble and by quid with some general advice for situations like this. (Although several paragraphs are about the specific situation of the OP.)

As a side note - would it perhaps be reasonable to create serial-voting tag on meta? (For example, by adding it to the above posts.) It would make finding relevant questions easier in the future. And the tag-info would be good place where to collect pointers to the relevant information.

Speaking of meta tags, looking at the ones which have been created recently, I am not sure whether funny, set-theory and large-cardinals are going to be useful tags on meta.

@T.Amdeberhan Our tools for investigating serial or vindictive downvoting are somewhat limited. Do you have an estimate of how many such downvotes there are? I did see one user who cast 5 downvotes on posts attached to your account, but I don't know which posts they were, and I myself wouldn't jump to the conclusion they were vindictive, although of course they could be.

@T.Amdeberhan Site moderator tools don't allow us to see which posts are upvoted or downvoted; it just gives a number (and not for all users either). But there could be other clues. If there seems to be a detectable pattern of abuse from someone, then a moderator message can be sent.

@T.Amdeberhan More effective might be to contact the StackExchange Community Management, as they have stronger tools. If you scroll down to the bottom of any MO page or your user page, you will find a box in gray, with a button to push 'contact us'. You can reach them that way.