@sturmsucht @oblomov @dansup Mastodon added a ton of non-specified on top of ActivtyPub. PixelFed is recently partially compatible but it’s got its own layer on top of AP.
Protocols on the internet are layered. We’re talking about layers within layer 7.
https://en.m.wikipedia.org/wiki/List_of_network_protocols_(OSI_model)