The abuse I predict is someone tagging every node by merlyn as "bull..." and other rude, abusive, and obscene tags being thrown in because that's what many children are prone to do when given an anonymous way to scribble on the walls.

Adding a keyword is so trivially easy while finding the offense, considering it, and getting a privileged user to remove it, is severals times more work. So I bet that increased visibility of the keyword system will eventually lead to an annoying amount of abuse.

Which reminds me that part of thee value of voting is abuser correction, not just abuse correction.

One idea would be a non-XP point system whereby adding keywords that get downvoted cost you points such that you can't add keywords as frequently...

I'm not saying your patch shouldn't be applied. But I personally wouldn't spend time implementing a privileged keywording group and would be prepared for the keyword system needing to be disabled until a major overhaul happens.