I thought the term "Fediverse" specifically referred to software that uses ActivityPub to federate content across instances. Like how Git is decentralized, but it's not federated. Now I'm confused.
Also, messages travel trough Tor, so you get P2P and identity. The coolest IM.
The hardest too, because you should only add contacts verified face to face. (Technically you can add remote contacts but they'll be marked as not fully trusted.)
Sort of. Briar can do private messaging. However, Briar also supports Blogs and Forms. The neat part is that it is totally decentralized with traffic going over Bluetooth, WiFi and Tor. It is designed to communication in situations where an advanced adversary is targeting a group. It can be used a protests and such.
The downside with Briar is that it requires that something is online always. You can setup a old phone as a mailbox but it is still inconvenient.
My wife and I can talk about our kids without having to worry about them finding the text msg as we use it as a backup msg app. We let our kids use our phones for games at times and well kids are kids and will go through shit they aren't suppose to.