URLs containing literal IPv6 addresses as specified by RFC 2732 (http://www.ietf.org/rfc/rfc2732.txt) aren't recognized as links automatically because in the regular expression for detecting them that is given in inc/parser/parser.php line 880 [] isn't allowed so e.g.
http://[3ffe:2a00:100:7031::1] isn't matched. We should probably add a separate part of the regular expression that matches such IPv6 addresses.