I ended up with one thread subscribed from the other day. I have the email notification off by default. What I noticed this morning is that unless the thread has a *new* post in it (new since the last time I signed in) it doesn't show up on the main page of MyFT. You have to click on "All Subscribed Threads", click the little box on the right of each one, then delete to remove the subscriptions.

As for not suscribing to threads, it seems that my default is "no email notification", which as I just noticed right now at the bottom of this edit post page is *not* the same as "do not subscribe". If you go to the Edit Options page of MyFT, you can set the default to "do not subscribe", then it will stop subscribing you automatically to every thread you reply to.