There are actually two separate functions: subscribing to a thread, and getting email notifications about it.

If you're subscribed to a thread in any way, with or without email notifications, it should always show up in your Subscriptions listing.

• If you choose one of the email options, whenever there are new replies to the thread you'll get an email (the kind you specified) and the thread will move to the top of your Subscriptions list.

• If you choose "No email notification," the thread will move to the top of your Subscriptions list as always. You just won't get any emails for it.

I haven't been bothering with email notifications, myself, because I'm usually here several times a day and I check my subscription list more often than I check my emails.