Is there a way to subscribe to a thread, with replying to it?

You mean like clicking on the Thread Tools button and selecting "Subscribe to This Thread"?

Never saw that at all.. I wasn't looking for a dropdown, but for an actual button.. thanks!

I had the same trouble with trying to figure out how to mark all the threads in a forum as read - was looking for a button, but it was in the "Forum Tools" drop-down.