The file tpl_account_default.php is currently using the constant SHOW_NEWSLETTER_UNSUBSCRIBE_LINK to determine whether or not to display the newsletter unsubscribe link in the customer's account settings. That constant is described as Show "Newsletter Unsubscribe" link in the "Information" side-box?. The correct constant to use in the customer's account settings is ACCOUNT_NEWSLETTER_STATUS, which defines whether or not to display the newsletter sign-up for the customer's account.

The current code, starting at line 65, reads:
Code:
<?php
  if (SHOW_NEWSLETTER_UNSUBSCRIBE_LINK !='false' or CUSTOMERS_PRODUCTS_NOTIFICATION_STATUS !='0') {
?>
<h2><?php echo EMAIL_NOTIFICATIONS_TITLE; ?></h2>
<ul id="myAccountNotify" class="list">
<?php
  if (SHOW_NEWSLETTER_UNSUBSCRIBE_LINK=='true') {
?>
and should be changed to
Code:
<?php
  if (ACCOUNT_NEWSLETTER_STATUS != '0' or CUSTOMERS_PRODUCTS_NOTIFICATION_STATUS !='0') {
?>
<h2><?php echo EMAIL_NOTIFICATIONS_TITLE; ?></h2>
<ul id="myAccountNotify" class="list">
<?php
  if (ACCOUNT_NEWSLETTER_STATUS != '0') {
?>