Hi David, the default is that you automatically "watch" a thread after you post in it. If you "unwatch" it (on right side, near top when you are in the thread on a computer or at top in middle on phone), you won't get notifications from that thread.
I think you can also change this in your account settings so it never happens again for all threads. You can do this in the "Preferences" Tab in "Account Details" when you click off the box for "Automatically watch content you interact with…"