In details.php find:
"comment_user_id" => $comment_user_id,
insert below:
"comment_user_admin" => ($comment_row[$i]['user_level] == ADMIN),
In template use:
{if comment_user_admin}style for admin{endif comment_user_admin}
{ifno comment_user_admin}style for everyone else{endifno comment_user_admin}