When you edit an existing gift certificate at /admin/store/gift_certificates/*/edit, there is a field for editing the Message to Recipient, but when the record is submitted, the change to this field is not saved along with the other fields. In looking through uc_gift_certificate.admin.inc, at line 326, the gift certificate record is updated, but the attributes in the order_product record are not updated.

I discovered this because I want to add more attributes to the gift certificate, and wanted to patch uc_gift_certificate to include these additional fields.