You know I'm a committed user of the fediverse, perhaps this post will surprise you. Still, at some point the truth has to be told, before lying leads to a catastrophe. I think I've been present in the fediverse (sometimes hosting a pod of some software and sometimes not) since
I’m surprised the author did not mention NNTP, the protocol that ran the larges federated discussion system since 1986.
ActivityPub reinvented NNTP with less efficiency and very poor documentation.
NNTP is hierarchical. Also it’s certainly not more efficient with it’s 7bit MIME header system. And at least all of the docs for AP are in a single spec and not spread to 100 RFCs.