That's a very theoretical problem though, isn't it? Individual comments don't have the length of books, and usually don't individually contain enough text to be

That's a very theoretical problem though, isn't it? Individual comments don't have the length of books, and usually don't individually contain enough text to be unique. Once the account-relationship is gone, it's essentially like splitting all the books up into paragraphs and trying to attribute individual paragraphs. Unless you're Wittgenstein or someone with a similar interest in exploring how long sentences can be, I doubt there's enough there. Of course, all of that is hardly useful, since HN is very open and lots of people have copies of all comments.