You can always add a link to a thread to your browsers bookmarks/favorites. There isn’t normally a reason to need to go back to a thread after you have visited it if there aren’t any new posts posted.
Funny you should say that--I just bookmarked DdmrDdmr's "
ranking up pipeline" thread so I can easily go back to it as a reference and not have to wait for it to get bumped ('cause I might just miss it when it does). And a couple of years ago when I was more interested in merit statistics I had that page that lists the most generous merit-giving members and so forth bookmarked. I don't even know how to access that one anymore, but my point is that it's easy enough to bookmark threads and put them in their own folder if there's enough of them and you want to keep organized.
I never got into using the watchlist function on bitcointalk, because I always thought it was much easier to just have a bookmark for a thread I wanted to follow. To each his own, however.