> Actually, just printing the indentation number (perhaps in parens) next to each comment subject line would be fine; I can Ctrl-F for the next comment with the same number in parens.
Have you mailed that in as a suggestion? I like it! =:^)
Meanwhile, IIRC there was an LWN firefox extension or at least grease monkey script. I've never tried it, but it could well have something like this, and if it doesn't, adding it should be reasonably easy, I'd think.