"Show new replies to your posts" is not a notification, it is exactly what is says. Notifications can be set to e-mail you when a response is added to a thread you are following. Most folks have notification set by default to any thread they create or comment on. In this case, you can "unsubscribe" from notifications, but the replies will still show in "show new replies to your posts".
Ok, the forum software is a little different from what I'm accustomed to.
Basically, either I accept all notifications of new replies to all threads I've posted to or either I opt for no notifications of new replies to all threads that I've posted to...have I got that right? It's either all or none?
I'm definitely still a bit confused on this, but no biggie.