You would need to edit the file:
And change the select statement to not include those that were not sent to the customer ...
This select is grabbing all of the history ...
$statuses_query = "SELECT os.orders_status_name, osh.date_added, osh.comments
FROM " . TABLE_ORDERS_STATUS . " os, " . TABLE_ORDERS_STATUS_HISTORY . " osh
WHERE osh.orders_id = :ordersID
AND osh.orders_status_id = os.orders_status_id
AND os.language_id = :languagesID
ORDER BY osh.date_added";