Comment 3 for bug 699760

Another possibility for "internal" notes is to use a distinct element in meta.xml (other than <notes>), and then not display that element on details pages. We already have a mechanism for skipping display of designated elements. That won't securely hide the information, but it will prevent casual observers from being exposed to it - you'll have to go looking for it (download meta.xml, or view the details page with output=json) in order to see it.

Also, we have some experience with attaching (patron-facing) <notes> from a pre-formed list. The ufilm workflow at one time included that feature (and may still).