An incompatible attempt at reformulating Mastodon Protocol. If you've ever actually tried to work with the protocol, you'll know the standard only loosely describes it. If you attempt to implement it by following the standard, you won't be compatible with anything else, because everything else implements Mastodon Protocol instead (and calls it ActivityPub).
Touché. Mastodon is the Internet Explorer of ActivityPub. There are other, non-Mastodon extensions, and some ActivityPub-spec functionality that Mastodon eschews but other implementations support, but overall this is an accurate summary. Especially regarding the C2S protocol: most apps just use the Mastodon API instead (see https://github.com/mastodon/mastodon/issues/10520).
