The automatic gratuity went into affect January 1, 2008. I think it was pretty unfair that those of us who bought the DDE before this change was announced not only had to take such a drastic change in our benefits, but that we were never notified! They certainly had all my information...email, street address, phone number....but not a single message telling me that the benefits had changed. My bank and credit card are required by law to notify me of even minutest "who cares" changes to our financial agreement....you'd think that Disney would at least have the courtesy to let people know (yes, I know they probably have no legal duty since they have the "subject to change" clause and it's not a fidicuary contract). If it hadn't been for reading DIS I'd have never known because not once did a server point it out to me my whole trip....but I knew so unlike you I never double tipped.
Ok vent over.
If you purchased your DDE before January 1.....you might write a letter telling them of the unfairness of the situation and request the extra 18% be refunded to you. You probably have a 50/50 chance of them agreeing...more because of PR than wrongdoing, but it would at least tell them that you didn't appreciate not being told.
Ok, after venting, also keep in mind that while the DDE card is no longer really a discount (after all giving me 20% off and then reclaiming 18% of it makes for a pretty dismal discount)...think of it as a prepaid gratuity. For an entire year, no matter how many meals you eat, you will never have to pay a tip again. You won't get a discount, but you won't pay a tip. It's all in the way you think about things, lol.
