Interesting Joel,
when I googled for 'gnu arch irc' a few hours prior to your search the first 2 hits in thecodemill.biz domain were /services/arch and /services/arch/irc, NOT the blog entry that tops the search result set now.
The reason that you have to include the host header is because thecodemill.biz is behind a hostname based proxy: pound. In other words thecodemill.biz is a virtual server.
/Bart
