all you have to do is make a reply in someone's thread..
but then i also have all of my subbed threads show up in my roll it up.. this way, i go to my roll it up, and i get to see what threads i'm subb'ed to have no responses, and the newest ones rise to the top of the list, keeps things easy seeing what threads are active and which aren't..
give me a second, and i'll tell you how to do this as well, i just need to figure it out, lol..