He's right though that Twitter has a big advantage in that it's easy to ignore jerks. It might be a good idea to introduce some form of following or blocking here.
"And he put his arm around my shoulders and we went for a little walk and he said, Randy, it’s such a shame that people perceive you as so arrogant. Because it’s going to limit what you’re going to be able to accomplish in life. What a hell of a way to word “you’re being a jerk.” [laughter] Right? He doesn’t say you’re a jerk. He says people are perceiving you this way and he says the downside is it’s going to limit what you’re going to be able to accomplish."
I always think it would be interesting if that approach could be abstracted into a tool for online community 'civility management'. Could the upvote/downvote approach be amended? Could there be another upvote option for civility? A button to remind people to relax and take the angst somewhere else? I don't know. The best approach might be far removed from the users-as-voters paradigm.
One of the nice things that HN affords is that it doesn't really support filter bubbles--at least until mods or the community downvotes you to oblivion. Thus, there's a good chance that people at least get exposed to ideas they might otherwise ignore.
Hell, I can think of several posts where I've strongly disagreed with somebody else, only to be in jovial agreement or discussion a few days later. I'm not sure that a blocking mechanism is really needed; if people are being deliberate and abusive trolls, we have ways of dealing with that, right?
Let's be honest--usually, blocking (in a community which has other ways of dealing with abusive users) is just a way of helping people be intellectually lazy and filtery.
Maybe you can outsource comments moderation to a group of competing startups. Not for all posts but for 10% or 20% of front page posts. Maybe we will see a "pagerank" algorithm for comments or something more clever.
I don't think there's any reason to necessarily link it to banning or something, though. Just make it like a per-account killfile. in fact maybe you could even add regexes to filter out phrases or urls as well.