There is a pretty big difference between ignoring one commenter who doesn't like you and ignoring the complaints of a large proportion of the community. This wasn't just one or two people kvetching. It was a large number of people, including many (like me) not directly targeted by the behavior. I don't think you have any obligation to respond to gwern, but if a significant segment of the community objected strongly to your allegedly trollish behavior, and some valuable contributors said they no longer felt comfortable participating on LW because of that behavior, I would consider it "pathological disregard" for you to continue what you were doing as if none of this was happening, without addressing it in any way.
Keep in mind that Eugine continued (surreptitiously) with his block-downvoting not just after a number of users expressed their dissatisfaction, but also after the administration of this site made it clear they disapproved of the behavior. First Eliezer said that he was trying to track down the block downvoter (he failed for some reason), then Kaj put up this post. And Eugine kept down-voting. I don't see how this doesn't read as disregard for the community.
Perhaps he thought he was somehow making the community better by his actions (although it's much more plausible to me that he was just ridiculously mind-killed, since virtually all of the block-downvoting appears to be motivated by political disagreement), but he was still doing it in the face of the community's express wishes, and to the evident detriment of community relations. Thinking that his behavior would make the community better/more successful is so disconnected from the reality of what was actually happening that it qualifies as pathological disregard for the community, I think. Disregard for what people think and how they feel, and disregard for the observable consequences of his behavior.
Perhaps he thought he was somehow making the community better by his actions (although it's much more plausible to me that he was just ridiculously mind-killed
I don't see a contradiction here. If someone is mind-killed, then from inside it seems like all people with different political opinions are idiots, and the debate would be more rational without them.
Thus in my opinion Eugine completely failed in the lessons about mindkilling and ethical injunctions, and was incompatible with the spirit of Less Wrong.
As previously discussed, on June 6th I received a message from jackk, a Trike Admin. He reported that the user Jiro had asked Trike to carry out an investigation to the retributive downvoting that Jiro had been subjected to. The investigation revealed that the user Eugine_Nier had downvoted over half of Jiro's comments, amounting to hundreds of downvotes.
I asked the community's guidance on dealing with the issue, and while the matter was being discussed, I also reviewed previous discussions about mass downvoting and looked for other people who mentioned being the victims of it. I asked Jack to compile reports on several other users who mentioned having been mass-downvoted, and it turned out that Eugine was also overwhelmingly the biggest downvoter of users David_Gerard, daenarys, falenas108, ialdabaoth, shminux, and Tenoke. As this discussion was going on, it turned out that user Ander had also been targeted by Eugine.
I sent two messages to Eugine, requesting an explanation. I received a response today. Eugine admitted his guilt, expressing the opinion that LW's karma system was failing to carry out its purpose of keeping out weak material and that he was engaged in a "weeding" of users who he did not think displayed sufficient rationality.
Needless to say, it is not the place of individual users to unilaterally decide that someone else should be "weeded" out of the community. The Less Wrong content deletion policy contains this clause:
Although the wording does not explicitly mention downvoting, harassment by downvoting is still harassment. Several users have indicated that they have experienced considerable emotional anguish from the harassment, and have in some cases been discouraged from using Less Wrong at all. This is not a desirable state of affairs, to say the least.
I was originally given my moderator powers on a rather ad-hoc basis, with someone awarding mod privileges to the ten users with the highest karma at the time. The original purpose for that appointment was just to delete spam. Nonetheless, since retributive downvoting has been a clear problem for the community, I asked the community for guidance on dealing with the issue. The rough consensus of the responses seemed to authorize me to deal with the problem as I deemed appropriate.
The fact that Eugine remained quiet about his guilt until directly confronted with the evidence, despite several public discussions of the issue, is indicative of him realizing that he was breaking prevailing social norms. Eugine's actions have worsened the atmosphere of this site, and that atmosphere will remain troubled for as long as he is allowed to remain here.
Therefore, I now announce that Eugine_Nier is permanently banned from posting on LessWrong. This decision is final and will not be changed in response to possible follow-up objections.
Unfortunately, it looks like while a ban prevents posting, it does not actually block a user from casting votes. I have asked jackk to look into the matter and find a way to actually stop the downvoting. Jack indicated earlier on that it would be technically straightforward to apply a negative karma modifier to Eugine's account, and wiping out Eugine's karma balance would prevent him from casting future downvotes. Whatever the easiest solution is, it will be applied as soon as possible.
EDIT 24 July 2014: Banned users are now prohibited from voting.