I don't think there's any reason to punish someone for delevelling on purpose. Corpses fade after some amount of time, and you could get rid of them if you wanted.
I've seen a couple people delevel on purpose, mostly to get back to valk after they've left.
I disgree, this is a serious offense and must be punished: however the punishment must fit the crime.
To that end, Avalon should be raised 12 prime levels and 9 secondaries.
Wait.. make it worse. 13 prime and 10 secondary. That'll teach him!