Is this specific to the Mastodon implementation or is it in the ActivityPub protocol specification?
The Washington Post article linked in "Read More" claims:
Thankfully, this isn’t specific to Mastodon alone — this method is a standard supported by other networks, which means The Post can support verification elsewhere in the future.
However, after a quick Google search, it seems only Mastodon supports this. All results for "fediverse verify" only mention Mastodon.
That likely just means that none of the other fediverse projects has implemented it yet.
I know that Calckey and its descendants support it since I verified my account on a Calckey instance, and Akkoma mentions it in this blog post.
I didn't know Mastodon implemented a built-in way to verify your account, this is great news. For those who want to verify on other networks: you can use keyoxide.org for that - however it is a rather cumbersome process. But I know that the developer (@yarmo@fosstodon.org) is aware of it and aim to make it more easier to verify different accounts on different platforms.
