I am going to publicly call for banning user VoiceOfRa [...] VoiceOfRa almost certainly downvote bombed the user who made the grandparent comment, including downvoting some very uncontroversial and reasonable comments.
Consequentially...why bother even if this is true?
Assuming you are correct, Eugene's response to being banned (twice!) was to just make another account. It's highly likely that if you ban this new account, he will make a fourth account. That account will quickly quickly gain karma because, as you note, Eugene's comments are actually valuable. You are proposing that we do the same thing a third time and expect a different result.
Possible actual solutions that are way too much work:
move LW on to an Omnilibrium like system of voting where Eugene's votes will put him strongly into the optimate cluster and won't hurt as much.
give up on moderation democracy on the web.
How does Omnilibrium voting work?
Another month, another rationality quotes thread. The rules are: