In reply to Darkinbad:
I've mentioned it on here a few times but my knitting forum has some great functionality for this sort of thing. A post has a link to what it's responding to and if I click on it it displays that original post within the one I'm reading. That embedded post is also linked back to the one it itself was in response to so you can see the entire train of a conversation without navigating away from the original post.
In addition, once a post has been replied to it displays the number of replies it's had so you can also open those up within the post. It's great for when you're halfway through a long thread and you spot something you want to respond to, means you can immediately see whether a load of other people have already made the same point.