normalize domains as usernames
Normalize domains as usernames is the idea that we should encourage and expect more people and services to use domains as usernames, instead of usernames that are local to a single service and don't have any meaning or use outside of that service.
Web sites are the most obvious example, with the easiest way to access them. Just type a domain into your browser's address bar, and you'll go to that person's web site!
Social networks and services are starting to use domains internally as their own usernames. micro.blog has been doing it for years. More recently, Bluesky is now doing it too.
The new user signup flow is a critical pattern here. If a services uses domains as its usernames, it should ideally include domain registration as part of its signup flow, make it just as easy as choosing a non-domain username, and crucially handle any DNS setup behind the scenes, without requiring users to know DNS at all.