Making Comments, a sub_menu in admin menu

Well one way to do it would be to add a new sub menu page and just remove the old one.

function wpse_80457_menu() {
add_submenu_page( 'edit.php', 'Comments', 'Comments', 'manage_options', 'edit-comments.php'); 
remove_menu_page( 'edit-comments.php' );
}

add_action('_admin_menu', 'wpse_80457_menu');