Do you have to link manually from a blog entry to the comments?

Yes, but it's just a matter of pasting in an a href with the URL, or a bit of code to fiddle with to get the comment count. Pretty simple.

(One of the useful things about Quick Topic is that when you're logged in, you can see comments you made in other people's threads as well, not just the ones you created, on your My Topics page. Since no one else seems to use it other than Boing Boing, though, it's not that useful...)