I'd like to see a hidden field that can be added to all members profiles, which can only seen by moderators and admins. When a member seems to be causing problems, a moderator can tag the member and all moderators and admins can easily track their posts for a specified amount of time without their knowledge. Sort of like putting them on probation.
I'd think that the warning system hack is a better version of what you are looking for, because everyone has different levels of warnings, depending on how bad they are. It would show to your staff who's been behaving worse than others.