For instance, how could you know what someone's reaction to an action would be before you make it, whether it would increase or decrease utility?

As I said, I am sckeptical at the very notion of utility. First, how do we ever arrive at such a metric in the first place? If any thinks that he acts ethically while taking as a guide his hedonic calculus he may very well be in great error as then he bases moral assertions on sense perception.

I've never read of Hoppe before and the list you provided is very interesting! It's also good to hear that he makes no appeal to utility as it seems nowadays most of the thinkers are infuenced by the notion more or less.

I'll investigate him further!