function plt_hide_add_pingbacks_menus() {
//Hide the "Comments → All Comments" menu.
remove_submenu_page('edit-comments.php', 'edit-comments.php');
//Hide the "Comments → Add Pingbacks" menu.
remove_submenu_page('edit-comments.php', 'add-pingbacks');
}
add_action('admin_menu', 'plt_hide_add_pingbacks_menus', 11);