Running 1.5.0, no mods. There is hardcoded text in \YOUR_ADMIN\stats_customers_referrals.php, lines 151-152:

Code:
            <td class="main" align="left">Order #<?php echo $customers_orders->fields['orders_id']; ?></td>
            <td class="main" align="left">Discount Coupon ID# <?php echo $customers_orders->fields['coupon_code']; ?></td>