@fediversereportConnected Places
The Mastodon API is open source, but it is not an open standard. It is designed, maintained, and changed by one project, without input from the rest of the ecosystem.
Not without. The design of this API is shaped by the needs Mastodon users. Sometimes PRs are submitted by developers of 3rd party clients and by developers of other servers. Independent implementers of Mastodon API often extend it, and copy each other's extensions, there is even a discussion about Mastodon API Enhancement Proposals (similar to FEPs).
So I think that by now it is very much an open standard.
ActivityPub API may have W3C's stamp or approval, but that doesn't mean anything if nobody uses it.
P.S. Does your blog not federate anymore?