On the osc forums there was a question about setting up the admin so you can add comments that are hidden from the customer.

Since I'm using an oscmax and resolved it with a five minute kluge I figured that I would add a reference to it here in case anyone here wants to make the changes. Please note that the changes to the user side should be made in you .tpl.php file not in the regular osc files.

Can You Keep (Private) Notes In An Order? - osCommerce Community Support Forums