Awesome, I totally just smashed this blog's comment facility into tiny bits while trying to add functionality to threading (which, as it turns out, doesn't quite work as advertised - but more on that when I actually have it fixed).
I have a better understanding of why Boing Boing and Making Lights' comments snap in half all the time while the rest of the blog features stay aloft. Movable Type seems to have an odd sort of duality with posts versus comments.
Update: Fixed, I think, with my intended improvement in place. Full nerdly explanation later. There's a bit of open-source lurrrv going on here.