Adding "Additional Comments" to the Catalog Task Form

I have a request for fulfillers to be able to post customer-visible comments on the catalog task form rather than having to navigate to the requested item to post those comments. Since catalog tasks are not customer-visible, the comment ultimately needs to go on the requested item. I thought I would simply show the Additional Comments field on the catalog task form and create a business rule that when someone posts a comment on the catalog task, the comment gets copied to the requested item, but I cannot figure out how to show the Additional Comments on the catalog task form. I tried modifying ACLs to do this, but to no avail. Any idea how I can implement this?