For me subscribing to threads isn't all that different from bookmarking those threads because I have the e-mail notification turned off. I guess if you post in a lot of threads like I do it might be hard to find one favorite thread, but I guess you can always just bookmark the thread in your browser ( if you use chrome you can log in and have your bookmarks at any computer).
That is not a solution. Sounds more like a work around. I prefer to get noticed by e-mail from my threads and I would also like to be able to bookmark interesting threads so that I have a chance to find them again.