I've read a lot of threads regarding use of vouchers and tips, and I do wish that it was clearer that the vouchers INCLUDE tax and tip - and a nice tip, too. I waited table for 10 years, and I would have traded the 'whatever I feel like giving you' tips for a guaranteed 15% or 18% anytime.
The reason that some servers really work hard to make sure that you get the most expensive things on the menu when you use vouchers is that they are tipped out on the final bill (the voucher portion) - so it's in their best interests to jack the bill as high as it can go. The OP's server may have had to eat the cost of the appetizer he incorrectly gave to the OP (maybe, maybe not - it depends on the restaurant).
And I think that one of the reasons that some servers get pissy when vouchers come out is that they are tired of seeing so much food go to waste. For instance, I had a long conversation with a server at Beaches and Cream last time I went, and he told me that the staff there was VERY happy when the Kitchen Sink was removed from the vouchers. He told me that tables would come in and order one for each person, no matter what their server tried to tell them, and of course, they would mostly just get left. A huge waste, and a fiscal burden that was NOT expected, but to WDW's credit, they honored the requests until the new voucher year. And I've read many many posts where the overriding theme was 'look at how much we got, we couldn't eat half of it, but what a bargain!'. Of course, it's legit, but having worked in the industry, I can see that it gets old after a while.
Not that the OP ordered too much food - frankly, I have 3 teenagers, and there's no such thing as too much food in MY house! I do understand what the OP was saying - I'm just responding to subsequent posts.
KC