I noticed the PetforumsUk site appears to have just removed any option for direct messaging (ie no icon at the top). Although they have left profile posting on (which I've never used previously). Edit: Wrong - they still have Conversations - it's just not obvious and in a nested menu.
So at the moment I'm thinking of a halfway approach to that suggested above
1) No DM's (not even to admin).
2) Keep existing report system (due to the way I have it set up with crowd moderation).
3) Keep existing private node for moderators
4) Add a forum node "Issues or problems and how to contact a moderator" With a post in there saying you can start a post here if you want a moderator response, or you can use the contact us link if you want a private response.
So the new node becomes a kind of chat node for off topic things, queries etc. I already have a "Suggestions" section. I doubt it would get used much.
Additionally the reporting system would be the main thing as that automatially sends posts for manual approval and on checking, you can tick to send a response to the reporter (even though that's a bit impersonal). Reports are unlikely to be about anything other than spam anyway. If a member has an issue with another member (unlikely) they can use the contact us link.
I would prefer to keep DM's just for contacting a moderator or admin but the permissions arent' extensive enough IMO to achieve that. There is an addon for "contact staff only" though.
But am also thinking it might be easier to just have DM options completely removed and no envelope icon - is that possible?
Another brief query, having had a group on Instagram recently - is there a way to "pin" a post at all? I know you can sticky posts but when looking through "What's new, keep a post pinned to the top"?