Moved some posts into an older thread on the same subject.
There are actions that can be applied to users who meet a certain 'user criteria'. This criteria can be reputation based and the result can be something directly applied to the user or the user can be moved temporarily to a different user group(with less privileges etc).
There are a LOT of possibilities. The thing is, the more you tweak, the more you have to check each time there is an update and anything to do with permissions, particularly those which are custom modifications which meddle with the default behavior, these tend to break right away when there is an update and this requires down time for that feature. For example we've had some user blocking stuff that hasn't worked in years and when it did, it didn't always work with all aspects of the site because we have many customization here. There are so many things to test its unmanageable for a single person to go through it all. So what I can do is implement some existing features like the one in this thread. Sometimes the perfect solution isn't one of the options however.