On Astronomy stack exchange I have only one item that people can vote on, a question from 2016. It was upvoted once that same year and gained another upvote in 2020. How can this be the target of serial upvoting? Today I got 1 such a correction for a score of -10, meaning that it must have been a short series.
Must I imagine that someone upvoted one of my contributions on another stack exchange site, then looked up my profile on astronomy stack exchange and found this question that was so beautiful that it also needed an upvote and that was it, and that's not allowed? Which is found out two years later? Is SE going to be like that?