I understand that I can read magazines from other servers, but can I post to them too?

I'm not new to fedi but I'm still trying to understand federation with these new projects.

I can sub to magazines/communities hosted elsewhere.

Can I also post there? I see them offered in the dropdown on this composition page so it seems like I can.

To be clear, I'm talking about posting to them with my current account, on kbin.social. Not going and making an account there.