Odd. As of 7/25 I began receiving notifications of new messages in Jobs, Discussions, etc., which I 'd not been receiving in some time, even though I've been a member here for a while and messages appear to have been freely flowing during that time.
Number one, was there a change here that caused this and, number two, is there a setting to only receive messages from specific topics? Ah, I see Notifications (?) module is being used. Maybe something happened there that all of a sudden enabled my notifications?
Well, adding a thread subscription is sure convoluted -- there's no "subscribe to this thread" on each node. And there seems to be a bug in the "Group Notifications" block -- it's linking to someone else's notifications' settings.