Downvotes in their current form are already used by bigots to anonymously silence marginalised voices (this is the reason why queer instances like hexbear or blahaj lemmy have them disabled). It shouldn't need explaining why making it possible to essentially temp-ban users without any moderator oversight is a horrific idea.
Heavily scratched liberal gets banned from hexbear for being a debate pervert and trying to start fights, immediately proceeds to call everyone there mentally ill
They got it back without participating in the auction.