I don't know that the argument stands with "feelings of achievement". I agree that you can't justify a moral infringement by taking pleasure in it, but upthread you were trying to distance the motivation from virtuous ones like curiousity and activism. Being driven by achievement is absolutely a virtue. I'd argue it's the same virtue that drives curiousity, and you've essentially just said exactly that ("the feeling of solving a puzzle is a 'rush of power'" s/power/achievement).