In kbin’s UI, on every thread you can click “more”, then “copy url” to see what the origin of the thread is - if it shows another domain name like lemmy.ml then you know you are looking at a thread that originated on a different “fediverse instance”. Likewise you can also look at the URL of a username to see where they are posting from.

Lemmy presents things a little bit differently from kbin, and when things are federated to different instances there’s no guarantee we see exactly the same things as each other(voting stats, replies etc.) What we do get is roughly enough to have a discussion, though.