Banning the user is really not the way to stop this from happening. CGT should make the thief return all earnings made to the original artist.
I keep talking about revenue sharing because with it, this kind of problem would disappear.
You see as bad and annoying as this thief is they have much needed skills that if put to use in a constructive way could benefit us all.
If instead of stealing others models and selling them they could earn money from selling those models legally then they would loose interest in doing (bad things and illegal things) because they could still make money legally.
By working together the original seller actually would make much more in percentage without having to worry about making good renders, wire frames or providing proper info about their models.
Really good modelers should just be concerned with creating beautifully crafted models, just like sales people should be in charge of selling. This thief is your typical used cars salesman who found a way to cheat the system. I bet he or she sold a boat load of models!
All that money should go back to the original artist!