@Crispin I'm not positive that this message went to you correctly so I'm using a private post to redundantly ensure you get it.
I saw you tried to create an account on this server. Sorry that it didn't work out. Maybe you mistyped an eMail identity? I deleted the four similar attempts in case you wanted to give it another go. The sign-up process sends a default random password to your given email address so the email address must be typed accurately.
However, you need not have an account on this server to interact with it. That's the beauty of the Federation. The main difference is you can't easily filter down to the posts on the local community of a server that you don't have an account on. Not really a big deal. My servers have the public posts available on the Community page for the server anyway.