Ok so he doesn't have to manage it himself, he could employ a team. Great, so how much is Stephen going to be paying to this team to moderate the content of his 12.4 million followers? A dozen people? A hundred maybe? It sounds like an expensive venture.
He could just use the tools that come with the service. Tools that could filter out words, phrases that he chooses to omit or he could choose to disable replies altogether. He can also choose who gets to follow him based on certain parameters. I'm pretty sure if better minds than mine chose to solve this problem, they can.
BTW the site you are currently on has two moderators.
Why do any of those things require a "federated Twitter"?
Hackernews has two moderators and several orders of magnitude fewer users. I would argue that the amount of moderation required increases exponentially with the number of eyeballs.
Ok, so once users discover 1990s leetspeak what happens then?
Better mind than yours have chosen to solve this problem, they work at facebook and twitter and it's been a disaster! Twitter has been impotent, and facebook have been a public danger. The hard truth of it is that HN just isn't a scalable solution. It ropes in users to self-moderate which results in some really unehealthy issues at scale.
