Some goofball has been serial upvoting me for the past two days, and while I've sent out hunting parties to find the miscreant and taze him bro until he quits, I did notice an extreme oddity:
When the serial upvoting was reversed, instead of losing the 90-100 rep I was expecting to lose, I lost zero.
I know that I didn't actually lose any rep, since before "Serial upvoting reversed" I had 40,119 reputation, and now I have 40,179 reputation after having had six answers upvoted afterward.