Bernice: Well, sadly it is true.

Anyone can create as many accounts as they wish although it is strictly against stite policies. Although Fencer can not always determine if accounts belong to the same person. If the person chooses not to say anything to anyone, then no one would ever know.
In your case, if tthe person is openly admitting that they are banned then IMO they should be remoeved, BUT often it is not as easy as that