It's a truth universally acknowledged, that every comment thread hanging off a blog entry sooner or later veers away from the original topic and ends up approaching a stable orbit around the usual strange attractors of the blog commentariat.
For example, in the last-but-one blog entry, over the course of 350-odd comments we veered from a not-a-manifesto about urban fantasy to the subject of future transport tech in a post-global-climate-change world, and thence to a discussion of Californian aquapolitics.
There is of course a reason for this phenomenon. In general, folks who use the comments do so either to express an opinion on the original blog entry, or to carry on a discussion. As the volume of comments expands, most casual readers skip past them to deposit their fragrant opinions on the original essay—but the folks who are there for the discussion read all (or most of) the comments, and participate in the top drift. As the volume of observations on the original entry dies down, the comment thread comes to be dominated by the ongoing discussion: which is to say, it's perpetuated by the usual suspects, who continue to focus on their usual subjects.
What are the usual strange attractors for this particular blog? Discussion of this topic is welcome, and encouraged! (But discussion of the strange attractors themselves may be moderated or deleted, lest this topic vanish up its own recursive arse.)