This sentence is just explaining how he thinks Mastodon usage will evolve, comparing it to federated email instances and the protocol they use to communicate (S

This sentence is just explaining how he thinks Mastodon usage will evolve, comparing it to federated email instances and the protocol they use to communicate (SMTP). Most people who use email don't know that, and most people who use Mastodon don't know its federation protocol either. Most people who read Fowler's blog or HN are able to understand the difference between what users need to know and how a system is implemented.