Unfortunately, having the constants in the checkout_success page's language file doesn't do the order_status page any good.

Those two constants are used at the bottom of tpl_order_status_default.php:
Code:
<!--Kills session after COWOA customer looks at order status-->
<?php
if ($_SESSION['COWOA'] and COWOA_LOGOFF == 'true') {
  zen_session_destroy();
} else {
  if (isset($_SESSION['customer_guest_id'])) {
    echo TEXT_CHECKOUT_LOGOFF_GUEST;
  } elseif (isset($_SESSION['customer_id'])) {
    echo TEXT_CHECKOUT_LOGOFF_CUSTOMER;
  }
?>
<?php } ?>
<!--eof logoff-->
I'm thinking that the wording on the order_status page should be a tad different than that used on the checkout_success page, too.