i think a good middle ground for letting people to have private discussions on fediverse is just allowing people to do PGP themselves or in 3rd party clients, with a "buyer beware" kind of scenario
building it into servers puts a lot more responsibility in the hands of server admins. and risk for abuse. i don't want my admin holding onto my private keys and i don't necessarily trust my server to generate keys for me either ...
people with the know-how to generate and manage their own keys can deal with the potential negatives and headaches associated with it. just running servers as they already exist is plenty of work for mastodon admins i would imagine
