However, you can flip this over trivially and come to a terrible conclusion. If Duplication is true, you merely have to simulate a person until they experience a moment of pure hedonic bliss, in some ethically correct manner that everyone agrees is morally good to experience and enjoy. Then, copy the fragment of the simulation covering the experiencing of that emotion, and duplicate it endlessly.

True just if your summum bonum is exactly an aggregate of moments of happiness experienced.

I take the position that it is not.

I don't think one even has to resort to a position like "only one copy counts".