Is there any way to delete threads from your list

You can select the thread in question and hit the Action drop-down menu. Hover over the "Mark as Read" title, then it should show another menu for how long to mark it as. If you don't participate in a thread for over a week, it will leave automatically, so if you choose to keep it marked as read for a week or month, you will not be notified whenever someone replies in the thread. It will still be there until the week is over, but you won't be notified about it.