Agregar este codigo al final del archivo function.php de tu template :

 

 

add_filter('comments_open', 'restrict_users', 10, 2);

function restrict_users($open, $post_id) {
if (intval($post_id) && get_post($post_id)) {
$args = array('post_id' => $post_id, 'count' => true);
$user = wp_get_current_user();
if ($user && intval($user->ID)) { // for registered users
$skip = false;
$ignoreTheseRoles = array('administrator', 'editor'); // which user roles should be ignored
if ($user->roles && is_array($user->roles)) {
foreach ($user->roles as $role) {
if (in_array($role, $ignoreTheseRoles)) {
$skip = true;
break;
}
}
}
if (!$skip) {
$args['user_id'] = $user->ID;
$open = get_comments($args) ? false : true;
}
} else { // for guests
$commenter = wp_get_current_commenter();
if ($commenter && is_array($commenter) && isset($commenter['comment_author_email'])) {
$args['author_email'] = $commenter['comment_author_email'];
$open = get_comments($args) ? false : true;
}
}
}
return $open;
}

Te ayudó?