Following a Hacker News thread for new comments

It happens often that I find an interesting thread, read all the comments and keep it open in a tab for the next few hours so I can refresh and read new comments as they come in. The problem with this is that you never know where these new comments are, so you usually have to re-read lots of stuff before finding the new comments you're looking for.

I'm just wondering how other people deal with this and how do they track new comments to interesting submissions.