On January 1, 2020, Lowtax changed a setting so that unregistered users could not see the forum index. Anyone not logged in would be given the banpage because of '=' in place of '==' in a section of the code. This led to discovery of an ancient bit of radium code that changed 'unregistered user' to a homophobic slur. Jeffrey fixed the bug, but this load bearing slur will live on forever.
While details are scarce at this point, my best assumption as to what happened hinges on the idea that non-logged-in users with a presumed username string value of unregistered user were meant to be forwarded to the login page, but because a separate section of the code changed the string value of unregistered user to [homophobic slur here], hence nobody actually got the correct forwarding and they were all sent by default to the ban page. If I recall, this led to the unintended side effect of non-logged-in users being unable to log in.