Recently, I've downvoted an answer and added a comment. After submitting my answer to the same question, I noticed that the downvoted answer has been upvoted (within 2 minutes, probably a sympathy vote, I thought).
I added more explanation to the downvoted answer, because the answerer believed that his answer was correct. A few minutes later, I received a downvote for my top upvoted answer.
My answer became accepted, for which I received another downvote.
I verified (Data explorer) that the specific user did not add new downvotes. So, I suspect this user of having a sock puppet, since the order of events were too coincidental.
However, since the sock did not upvote the owner's post, flagging the post will probably not help.
So, how can moderator's attention be requested for this case?
Reputation mutation (the times do match):