So, he/she was back last night. All of us talking about it on an open forum is going to do one of two things:
1 discourage the person so much that he won't want to post here again.
2. Massage his ego to a point where he can't stop himself.
I would hazard a guess that it's the later, he/she is getting much more enjoyment out of using the name Kanga because of the reaction it provokes.
We can't do anything (at the moment) about him/her logging on with an alias but would suggest that if it is obviously him/her then any complaints should be sent to the Mod direct (email). This way he isn't getting the attention he craves.
Just a thought.