Proposal for the others in the league: To close out the playoffs, 1st and 2nd place play for the undertitle. 3rd and 4th place play for the right to give last place an avatar of their choosing for a month.
(I realize that 2nd gets screwed that way, since 3rd gets a "prize" of sorts and 2nd doesn't, but it keeps the game interesting for more people for longer. 2nd at least has their shot at the best prize all the way up to the end.)
Edit: certainly for the best since a poster getting banned in midseason could have bad implications for the league. In a free league, high likelihood of abandonment and consequential fallout.