Maybe a bit naive, but what is the way that things that are going? What would Canonical pulling the rug out look like?

You mean if it is crossposted from Mastodon?

Same here, not sure if this is down to lemmy.world not federating with Mastodon instances or just if it isn't supported

Completely different topic, but if you put a hashtag on a Lemmy post or comment does it appear on Mastodon?

Gonna test it out, #testingthefuckoutofthis