You and paulfchristiano seem to be using the word "way" in two different ways.

Your post makes sense if I replace "the way" and "how" with "the direction in which". His makes sense if I replace "the way" by "the means with which".

To apply your example: I can't consistently prefer a value change like "I should eat more fish", because if I wholeheartedly preferred that then I'd already be eating more fish. I can prefer a value change like "I should eat more of whatever foods are recommended by good nutritional studies that I haven't seen yet", because although I cannot identify any specific failing of my current values I can identify that there are specific ways in which they might be improved in the future by unexpected new information.

This possibility of improvement applies only to instrumental values and self-inconsistent terminal values, but that's still pretty useful. How many people currently have and can unambiguously define self-consistent terminal values?