Would it be possible to number each post in the threads? That way referencing certain posts, especially in the big threads would be easier. It would also be useful for quickly locating where you left off when you revisit the threads the next day or something.
I was actually thinking of numbering them 1,2,3,4,5...etc in each thread but I can see the appeal of your way too. If you provided the post # for reference, could someone simply type that # into the search box & be taken right to it?
instead of displaying the number, you can have a small image (of a link? as in a chain?) which has image alternate text of the post #, and it can be a link to that exact post that you could copy to paste for other users