Wow Ian, it looks really good, but I do have my doubt about the per paragraph commenting. Won't more than 4 or 5 comments on a single paragraph completely ruin the layout of the page?
It can be difficult for the layout. They should just extend downward, but it gets bad when there's lots of comments on one paragraph, and then a comment on the next paragraph. That's ugly. The folded view might be better, or maybe some overflow thing, or otherwise combining comments. Really long comments (which can be very useful) will also cause these problems.
I also want to add a better interface for commenting on the entire page, probably presented as a simple list of comments at the end of the page. Or maybe threaded.# Ian Bicking