Great point about Goodhart's Law. Our eternal and tireless enemy. The best defense, I think, is internal cooperation. Stop self-deceiving by giving elements of yourself reasons that matter to them not to deceive other elements, and by giving them reasons to cooperate.

I almost say just that; the dance floor is only where the most overt type of dancing takes place. Did you really just say that its not a dark art to stretch your neck further than you voluntarily could by using an imaginary hook to pull your head up?

Good heuristic; if pot makes you better at it, its a 'dark art' in the sense of drawing on non-deliberate thought but not in the sense of moving you towards less accurate beliefs, and it won't feel evil but will feel aesthetically right. If pride motivates or empowers it its a dark art in the latter, worse sense of moving you away from truth. If deliberative thought helps the performance, not just the training, it won't corrupt you but it will feel cunning/tricky/evil even when you are good at it.