I also think that anonymous downvotes would be helpful. But while it may be possible to do it, there's no obvious way to do so. I will give it some thought though, since I need to solve a related problem for the reputation/rating system I want to develop: I want there to be a way for people to report negative ratings without being the potential subject of retaliation. I do have some preliminary ideas along those lines, but I'm not sure how easily they can be translated to Hive's reward system.