@simon The actual addressing of simon(a)simonwillison.net is independent of Mastodon though – it’s WebFinger which @blaine intially described and which has been around in this setup since @evan and @walkah created OStatus some +10 years back. And WebFinger can be used to discover a lot else, eg used by OpenID Connect but can really contain any kind of link relations, like eg rel-payment for a donation feature (we did back then at Flattr)
One of the most interesting innovations that Twitter gave us which I don't think is appreciated enough is the ability to reference a human being by a single, globally unique identifier
Being able to say "I learned this from @..." or "This project by @... is really cool" is such a neat way to be able to interact with the world
It can be abused too, but I really loved that ability to reference other real humans
We get that on Mastodon too, but only for the people who've moved here so far!