1) sale/order_list.tpl
1.1)
Ищеш
<form action="" method="post" enctype="multipart/form-data" id="form">
<table class="list">
<thead>
<tr>
И между <tr> Вставляеш в нужном месте <td>Комментарий</td>
1.2)
<td class="right"><?php echo $order['order_id']; ?></td>
<td class="left"><?php echo $order['customer']; ?></td>
....
<td class="left"><?php echo $order['date_added']; ?></td>
Там где тебе нужно дописиваеш
<td><? echo $order['comment']; ?></td>
2) Файл controller/sale/order.tpl
Ищеш Примерно 300 строка
$this->data['orders'][] = array(
В этот масив дописиваеш
'comment'=>$result['comment']
3) model/sale/order.php
Ищеш
public function getOrders($data = array()) {
$sql = "SELECT o.order_id, CONCAT(o.firstname, ' ', o.lastname) AS customer, (SELECT os.name FROM " . DB_PREFIX . "order_status os WHERE os.order_status_id = o.order_status_id AND os.language_id = '" . (int)$this->config->get('config_language_id') . "') AS status, o.total, o.currency_code, o.currency_value, o.date_added, o.date_modified FROM `" . DB_PREFIX . "order` o";
Меняеш
public function getOrders($data = array()) {
$sql = "SELECT o.order_id, CONCAT(o.firstname, ' ', o.lastname) AS customer, (SELECT os.name FROM " . DB_PREFIX . "order_status os WHERE os.order_status_id = o.order_status_id AND os.language_id = '" . (int)$this->config->get('config_language_id') . "') AS status, o.total, o.currency_code, o.currency_value, o.date_added, o.date_modified,o.comment FROM `" . DB_PREFIX . "order` o";