Shadow -- The point is to have the best of both worlds. So a person could join the Lemmy instance and participate in all the Federated communities. Then, they could be vetted for the private community (which is not Federated -- only on that instance), in order to discuss more private matters.
Not extremely secret stuff, more along the lines of "I'm a psychotherapist and I'm having depression issues myself" or "I have a depressed 23-year-old female client with symptoms of ..... Do you all have some treatment recommendations". Stuff that is back-channel and maybe the whole world should not read.
Despite their various evils -- Facebook, Tumblr, and Reddit all have both open and closed communities. Of course these platforms are no doubt reading the "private" communities and monitizing it quietly in some way. Maybe even selling the data out the back door...
Anytime people need a bit of trust and privacy at a distance this becomes a good idea. A young mother's group wanting to exchange advice and support on breastfeeding, an LGBTQ group at a particular somewhat hostile college in Texas, etc.
Yes, old-fashioned BBS systems (remember FidoNet?) do this -- but then non-technical people have to learn a new BBS login every blessed time they want to access one of their particular closed groups. So you do it all through Lemmy for some convenience.
-- Michael
Geronimo writes -- "I’ll see if there’s any existing discussions about private communities while I’m at it though, it might be something the main devs have an opinion on or plan for."
Brilliant -- thank you for checking.
There are all kinds of situations in which a (usually small) group of people might need some privacy. An oppressed minority at a college in the southern United States, a group of employees trying to unionize, etc. Doctors discussing procedures and needing both vetted credentials to comment intelligently/safely and the general public to not see they are disagreeing with each other...
At the same time, it would be great to have FEWER login credentials -- so members of these private communities could also partake in all the advantages of the Federated communities on their same Lemmy instance.
-- Michael