Hopefully, this will improve eventually, so that people have full sovereignty, also for moving between instances. Should be like changing your postal address, not your passport.

This is especially apparent when a community may operate multiple software, such as offering both Mastodon and Pixelfed, for their members.

Instance: internal node

People (or actor): leaf node

I think you have to start with instances, but I don't think you call them that. An instance is a technical term that is completely meaningless to almost everyone.

Call it a Community.

That's the core of the hierarchy.

• A Community decides to host a Social Platform
• That Community selects the types of content they want to share and then runs the appropriate software (Mastodon, PeerTube, PixelFed, Friendica, etc)
• That Community enables its members to join via the software they've set up
• That Community can then communicate with other Communities via the protocols available (ActivityPub)

The software is really secondary here. A community could run multiple pieces of software for their own purposes. In fact they probably should. The CBC Community should run both Mastodon and PeerTube.

It's not "one instance", It's a community running instances of all of the software they need.

I know you have an option for "people", but I don't think that is specific enough. It's "Communities of People".

But then I'm assuming you want to show the data flow, how the connections work between people and how those connections can fail or be blocked.

E) All of the above.

You can do the one diagram, but different copies with the different words, then stack them all on-top of each other to make the Fediverse

Being a literal-minded person, I chose Instances (/servers) because that's what handles the data.

But an alternate graph might be best described with hashtags.