This feature allows admins and group owners to define default category and tag tracking levels that will be applied to user preferences automatically at the time when users are added to the group. Users are free to change those preferences afterwards. When removed from a group, the user’s notification preferences aren’t changed.
Honestly looks very nice and solid to me, which is impressive for such a large PR.
I do wonder if we missed an opportunity a long time ago to centralize more of this logic using STI or something, but I suppose that ship has sailed