Hello, you might have noticed (or not) that posts from kbin, more specifically kbin.social aren't showing anywhere, this is due the DDoS protection they currently have on. So even if you are subscribed to kbin.social communities you won't see any posts from the outside.
Same is happening inside kbin.social where users there cannot see posts from the outside. This is however temporary and the admin is working on getting federation back online.
~~The site is currently reporting 125k registered users~~
Edit: After a quick chat with the dev group it seems this number is just the total users discovered by this instance. The real amount of users is 22k as seen on https://kbin.social/nodeinfo/2.0
Edit: kbin.social is currently upgrading servers to handle the requests.
My understanding believe kbin federates with three rest of the fediverse, (activity pub?) including Lemmy and mastodon, but not necessarily the other way around for their users.
From here, you should be able to see and comment to users on Lemmy insurance, as long as they are not blocking federation with your kbin instance.