I was slightly surprised to get all the way through the article without seeing a single mention of NNTP.
Spam as a term transitioned from, “flooding a communication channel with the same message” to “ads sent indiscriminately” due to a green card advertisement on NNTP.
What we need along with federation is federated moderation. There are some characterizations of content where we can agree to a label but not whether the label is bad. You might trust me to label gore accurately, I might trust you to label incitement to doxing. We might never agree on what constitutes baiting. Or the crossover point where a flame war should be filtered. So you might ban an individual who I think is “keepin it real” or vice versa. But ten of us shouldn’t have to do the exact same moderation in order to maintain a federation. N log n would be great, 3N would probably be tolerable.
With today's IRC user count and today's server capabilities, you might have an easier time running on a single server, but there's maybe some latency benefits for users with geographically diverse servers (maybe with support for a server to server mesh instead of a tree, to avoid multi-hop message paths)