At current version it could be implemented via small hack.
Open /components/com_jcomments/jcomments.php and replace code (twice):
."\n, v.value as voted"
."\nFROM #__jcomments AS c"
."\nLEFT JOIN #__jcomments_votes AS v ON c.id = v.commentid " . ( $my->id ? " AND v.userid = ".$my->id : " AND v.ip = '".$acl->getUserIP() . "'" )
with
."\n, v.value as voted"
."\n, case when c.userid = 0 then 'guest' else replace(lower(u.usertype), ' ', '-') end as usertype"
."\nFROM #__jcomments AS c"
."\nLEFT JOIN #__jcomments_votes AS v ON c.id = v.commentid " . ( $my->id ? " AND v.userid = ".$my->id : " AND v.ip = '".$acl->getUserIP() . "'" )
."\nLEFT JOIN #__users AS u ON c.userid = u.id"
And after that you need edit template: /components/com_jcomments/tpl/default/tpl_comment.php:
Add after line:
$commentBoxIndentStyle = ($this->getVar('avatar') == 1) ? ' avatar-indent' : '';
next code:
if (isset($comment->usertype)) {
$commentBoxIndentStyle .= ' usertype-' . $comment->usertype;
}
After that all your comments will have additional style like: usertype-guest, usertype-registered, ..., usertype-administrator, usertype-super-administrator