I may be completely wrong, but I thought the policy had more to do with people tipping to ensure better service, as opposed to those who tip as a thank you for services already received.
We've stayed in New York city many times and found that the concierges will make reservations and get tickets for you, but if you slip them a tip, the seats or reservation times will suddenly be much better. I thought I had read somewhere that Disney wants all it's guests to be treated equally, regardless of which resort or floor they are staying on. I'd agree with tipping, if it was a case of being thankful for outstanding service. For example, I tip mousekeeping for a well kept room, but I'm not doing it to make sure that we have a room full of towel animals. Threehearts, it sounds like your tipping was done as a thank you after a wonderful stay. Unfortunately, I've seen many who try to tip to get a better room with a better view, or a last minute breakfast table at CRT. As a manager, it's probably difficult to police whether an employee was taking a tip for an exceptional performance or because a guest wanted preferential treatment and enticed the CM with a generous tip. Disney's club level services are very different than what might be found at a Ritz or Four Seasons, so it's difficult to compare them.
I agree completely that if nothing else, great service deserves a letter to that employees manager. I have been told that they are taken into consideration at the employees review.