The idea is cool with all the apps interconnecting, but where do I go to actually see this in practice. Does the cross communication only work on platforms like Mbin/piefed, or am I not seeing something.
I keep hearing thanks to activity pub posts here can be seen and replied to from elsewhere, but I haven’t seen it.
Yes, Lemmy accounts can only follow/subscribe to groups (besides Lemmy also mbin, piefed + also Peertube), but not individual accounts. A Lemmy account can only communicate with individual accounts if they write something in a community. That is one of the aims of mbin, to connect them: The structure of communities /magazines + a microblog feed.