I’ll leave it to Timothy if he wants to address this, he shared his thoughts with me but I can’t speak for him, and wouldn’t feel comfortable trying to. 
The PM system on here, as I currently understand it, differs somewhat from other forum software in that it operates more as a “hidden thread” (hidden from other members) to which you can invite individual members, and which exists within the forum’s main architecture rather than being a kind of internal secondary system (no I’m no software expert, and I’m probably using the wrong terminology, this is my current understanding and information exists online for people who want to learn from experts - the software’s creator Jeff Atwood himself has made many posts regarding this. I’m on a learning curve regarding this as much as anyone, though I have used this software on other forums as a member).
There’s also a facility to form small groups of people to work on projects in small groups in relative privacy, though we ask that you remain within the Forum Rules when using messages on this site.
If you want to do this, you may need special access - PM me with questions.
Just as the old forum (with all its quirks!) needed an FAQ/user guide, I’m trying to put something together for the benefit of members, should be in the next few days.
Also, I’m currently updating some of the old pinned threads - this will sometimes result in them being bumped without new posts being added, I’m trying to do it while the forum’s quieter and I can’t see a way to prevent some bumps happening when I edit things to repair links or update information, so apologies for the - erm, dry bumping! 
- it’s a one-time only thing and I just want to make sure all the info & links are actually up-to-date & working.