As far as I can tell, I have ALL email notifications turned OFF. However I get email notif's for new replies in threads of the groups I am in.

Is there a special button somewhere I just don't know about? It's really annoying
Have you switched notifications off in the forum control panel, as well as on your profile?

If you go here: https://www.ultimate-guitar.com/forum/subscription.php?do=viewsubscription you should be able to remove subscriptions from threads you don't want to be updated on.

And if you go here: https://www.ultimate-guitar.com/forum/profile.php?do=editoptions you should be able to change your default thread subscription so that you don't get emails for threads you post in in the future, if that's what you want.
Populus vult decipi. Decipiatur.

Quote by Mistress_Ibanez
It's can be a contraction and genitive case.

Quote by Mistress_Ibanez
If you cut down on these costs students won't learn so well, effecting the "quality"...
I have switched all notifications off as far as I can tell. The thing is it's not for forum threads, it's only group threads.