Important thing to know if you weren't aware: people that you invited are connected to you on the server through the invite tree. If they cause trouble, this could potentially affect you, so don't just share codes publicly so anyone who grabs them first can use them.
To clarify since this got reposted: this information isn't public in the protocol so no one from outside can see who invited you or who you invited, but the team can see that and can take that information into account.
Thanks for the information.
My friend who invited me and I both carefully evaluate the people we invite to make sure the same problems that befell Twitter don't happen here. So far, so good.