Hmm, is it because your hackerposse.com/.well-known/host-meta points the LRDD to status.hackerposse.com/.well-known/webfinger?resource={uri} and thus ends the "acct:rozzin@hackerposse.com" to your #GNUsocial instance which doesn't know of that (without "status.") - and it should really point to its own domain?
(or one could allow a more liberal lookup, to include pre-configured domain name aliases or something)