Raise the Hammer

I daresay the auto-downvoting functionality goes against the spirit of the comment voting guidelines, but I don't see anything wrong with someone choosing not to look at something on their own copy of a page, and using an automated script to do the hiding.

The bookmarklet is a direct response to a situation where someone is clearly violating both the spirit and the letter of the commenting guidelines, as well as violating the spirit - the common law, if you will - of this community. That said, I don't actually feel good about creating it, because I don't feel good about any part of this situation or the emotions it has stirred up in this community.

The fact of the matter is that someone has made it their mission to harm this community by disrupting and ultimately destroying discussions here. They have not entirely succeeded, but they've certainly succeeded to a certain extent - after all, we're talking about it right now, and frankly we have better things to talk about. I'm not entirely sure why they've attempted to do this, but I would guess that they are frustrated by RTH's growing influence and readership.

That someone is trying to do this to the community that I love, and that I've been a small part of for so many years now, certainly bothers me. I won't delve too deeply into that, since this individual clearly feeds off that sort of negative emotion.

I do think that the best approach is referenced in your post, namely, "What makes trolls disruptive is not the trollish comments themselves, but the chain of outraged replies they manage to elicit." In other words, don't feed the troll. However, on a site that gets this much traffic, not everyone can be expected to know who to look out for; besides, the prolific commenting makes this approach more difficult to follow as well.

I find myself wondering if it would be a good idea to limit the number of comments a registered user can post in a given space of time. Perhaps the number could increase as a function of their overall comment score

Yes please. I think some of the ideas on Hacker News and Stackoverflow for dealing with trolls and spammers could be useful: throttling; overall comment score needing to be high enough to downvote in the first place; more substantial fading out of comments with a high-enough downvote level.