Not sure if this already has been reported. These lines in bbcode.inc.php:
if ($type == "post" && $config['NOFOLLOW_SIG']) {
$this->nofollow = 'rel="nofollow"';
} // end if
Should be corrected to:
if ($type == "post" && $config['NOFOLLOW_POST']) {
$this->nofollow = 'rel="nofollow"';
} // end if