Eriisa: They could be made a seperate class of User. They wouldn't appear on any lists of live Users. On games that they've played their profile link (if they even have one) could refer either to a Deleted User page which covers them all or to an Archived User page which retains some or all of the original information.

So a "purge" of this sort needn't affect any ratings or histories or anything. I think it would be welcomed by many people. It might severely impact on Fencer's project time, though.

Doing this could also free up a lot of names that people might like to use.