Federation is independent from content type so technically yeah, but seeing as you wouldn't really want to see microblog type content in a link aggregator style display... It doesn't really matter. Not to mention that afaik threads ain't even federated yet...
Yeah I figured there's a bit of an apples and oranges thing between the two, even if they use the same underlying protocol. On the one hand, it may mean there's less risk of threads poaching lemmy users/content (as compared to mastadon or even twitter), but on the other hand, there may not be much value in federating with them in the first place.
Mastodon, kbin, lemmy and all the other fediverse apps all use the same api, activitypub. This means we can all interact with each other even with very different ui and content goals. Mastodon doesn't interact with lemmy much right now because the uis don't really mesh very well, but it's possible. If you see a post that has @<community name> in it that's a good sign it probably came from mastodon or similar.
That's interesting. I have a mastadon account but I've never used it to try and get on lemmy. I have gone from lemmy to kbin though, even though I have a kbin account also.
Any service which makes use of ActivityPub should be able to federate with other services using the same. Hence why you can see posts from people using kbin. You can usually tell when a mastodon user comments because their reply will start with an @replyingto @originalposter