I have reverted the change to how integration/notification messagesYay, sort-of.
This still leaves events as a back-door around moderation, if members are allowed to create events. That could be significant for groups that rely on NuM to weed out spammers before they post.
I think this was the most straightforward solution, as you can useTrue, but this sledgehammer (applied to the #cal-... hashtags) would moderate invites, notices and reminders from all events, even "official" ones created by the group admins.
And it is a bit awkward, because the group admins must remember to apply it to all three of those hashtags. Or else have the strange situation of moderating one but not the others.
This situation points to the need for a moderation mechanism for the creation of events by members. I realize that implies several UI changes, including listing events in the Pending queue (or having a separate queue for them), and however you handle their display in the Calendar while pending (mods and creator only?).
Given that calendar events can be used to generate spam, I'd suggest that at least initially they be controlled by settings in the Spam Control section of the Group Settings. Moderate event creation by members if either Moderated or New Users Moderated is checked. Perhaps also disallow the "Subscribers can view and edit" choice in the Calendar control if the "Announcement Group" box is checked.