From the site:
Gift Certificate Summary
From this page, you can:
• Mark this certificate as "used"
• Remind yourself who you gave it to, if it was given as a gift
• Make notes for yourself on the certificate or restaurant
• View and print your certificate
Please note: This is a self-management system. A certificate will only be displayed as “used” if you mark it as “used.” This system is provided as a purchase management system only and is not update by Restaurant.com with the exception of adding certificates you have purchased.
Apparently, you need to keep track of which ones are used.
Reading is a right. Censorship is not.