I'm sure others can tell you about the Crystal Palace. I haven't been there, but I was shocked by the 18% gratuity for a buffet, too. But if you don't "latch" a credit card to your Key to the World card, and tell your server that you are paying cash for the tip (that is what we are doing) then there is no mandatory tip. We'll still tip about 20% if our buffet server is amazing, and really on the ball, but hey, if they aren't, there's no way I'm paying 18% for a buffet server tip. They will definitely be doing much less work. We also don't want any server thinking that they are getting an automatic 18% tip, so that's why we are telling them that it will be a cash tip at the beginning. Hope that helps!
You should also call back and ask to speak to a manager about the cast member's rudeness to you. They take that seriously. You are never supposed to encounter rudeness by a Disney cast member.
And yeah, I don't mind tipping that for a buffet, if it's worth it, but not if I have to.
How do I speak with a manager? And I have no idea who she was - I could barely make out the restaurant's names, she was talking so fast.