@atomicpoet @maegul that's only if both sides agree on at least a minimum of sensible information to exchange so that there is something to show for it. Can Mastodon do anything with a Place object? An Event? A Tombstone? Heck, Mastodon doesn't even go out of its way to support Article objects sensibly. We can argue that this isn't AP's fault, like it's not HTTP's fault that not all UAs support all image formats, but it is a limitation.
@atomicpoet @maegul and ultimately, this is a limitation that makes the platform more important than the protocol, because the platform is responsible for actually accepting the objects: you can't write a separate client that knows what to do with a Tombstone and have it display those objects that were sent to your Mastodon account. So platforms that want those Tombstones to be shown on Mastodon will end up sending Notes instead.