I've tried adding that but it had no effect.
I got it working but it required some extra steps:
// Have to set language, so that the order status (Confirmed) gets translated
// But we only have the locale from the GET array to work with
$lang = JFactory::getLanguage();
$langarr = $lang->getKnownLanguages();
$newarr = array_filter(array_keys($langarr), function($tag){
return (JRequest::getVar('lang', 'en') == substr($tag, 0, 2));
});
$lang->setLanguage(array_shift($newarr));
// Load classes
$userClass = hikashop_get('class.user');
$orderClass = hikashop_get('class.order');
// Load order
$dbOrder = $this->getOrder($order_id);
// Force reloading of language based on customer's language
// However, we're missing the order's customer info. We have to load that first
// I've tried use loadFullOrder, but it kept giving NULL
$dbOrder->customer = $userClass->get($dbOrder->order_user_id);
$locale = $orderClass->loadLocale($dbOrder);