First, thanks Kaj for doing your best out of a complicated situation. I'm op on some IRC channels, and I also know how difficult it is to take such decisions.

I don't think the ban was a mistake as a penalty (nothing prevents Eugine from creating another account, so it's not that harsh a penalty) but I do think it doesn't solve the main problem. The most important remediation would be to undo all of Eugine's mass downvotes, and if not easily possible, all of Eugine's votes. Any chance of that to happen ?