can someone explain me what happened with beehaw?

They defederated specifically with my instance (sh.itjust.works), and lemmy.world. What that means is that we can't access content on Beehaw, they can't access content on our instances.

If they see this post, my comment will be invisible to them. I can see their comments though, we haven't defederated with them.

They did this, as far as I understand it, out of a concern about our open user signups, where users don't need to be approved, they just need to not get banned. I have heard third-hand that there were some instances of hate-speech from users on our instances who quickly got banned (our instances don't allow that either, but it isn't pre-emptive), but they don't want the overhead and extra work for moderators.