I actually dipped a bit lower than my set goal today and expected a lot of fanfare or at least a congrats from the Wii, but it seemed to go unnoticed. Is this normal?

It doesn't get excited because it's aiming for your goal. It actually sees going below your goal as a bad thing. I suppose that if you were underweight and trying to gain it would be bad to be under so they have designed the game to accept whatever you gave as a goal as the place you're supposed to be. I have my goal set now to maintain and it tells me I haven't met my goal if I go under.