Err, I'm not contradicting myself. I am just arguing against different people. In certain threads, I am willing to defer argument on particular points in order to address the deepest point on which we disagree. The "asking for a less skilled waiter" scenario is simply a continuation of the roof-tarring analogy (which wasn't mine to begin with). I am not actually advocating that strategy, I am advocating tipping based on services rendered. The less skilled waiter supposition only applies to the scenario in which I am expected to tip whatever waiter I get based on the skills he has instead of on the skills he uses for me.
I know that most people can't follow discussions with this many branches. If you would like, we can continue this from a smaller kernel in another thread.