@Sam_uk, nice! Thanks. I was on an IP somewhere in the US (VPN). So maybe I got a different result today being on a different IP. At least I know what is going on at kbin.world now. It all makes sense :-)
Good question. Not ignorant. The one thing we use all the time but never think of as federated is email. Multiple users from different providers can reply all and everyone gets a copy. That is one way to help think about how the fediverse works. People using kbin and Lemmy have replied in this thread. We all see it. we are just using different providers/software to read and reply in the fediverse.