@feditips When I search for kbin.social instances on Mastodon, I can find the group, but they all show 0 posts. This is obviously not the case, because if you go to the kbin Magazine on kbin.social, there are indeed posts.
Similarly, if I look for a Lemmy community on Mastodon, I am able to see the posts from that community here on Mastodon. So, at least to me, it looks to be something on kbin's side.
Looks like it's federating, but some of the federation is broken? Not sure.