yo.com is its own proprietary server, that federates via activitypub but *ONLY* messages that comprise of a single two character sequence "yo", along with the user(s) they are directed to. This fact is not documented anywhere. Messages that are sent to/from this server to any mastodon/pleroma/etc server go through successfully but *only* the message "yo" can be sent. yo.com makes no pretense of supporting an open standard and encourages federation with other proprietary servers via proprietary protocols. Is yo.com on the fediverse?