Hi, thanks for this plug-in.
I'm very pleased to find it. We have just converted from a vBulletin forum where there was something called "miserable users" which was extremely useful. You have probably heard of it.
I run a very large forum – www.consumeractiongroup.co.uk and we need something like this plug-in from time to time.
The vBulletin version simply allows you to begin a new user group and any time you wanted to discourage someone, you put them into that user group and that was it.
The good thing about it was that it was extremely easy to check the identities of the people in the user group because they were thereby username rather than ID number.
If you are thinking of refining your plug-in more, then you might like to consider that as a suggestion. I think it would make it easier to use and easier to manage for administrators of large forums.