If you used the median then only actions which affected the utility of someone in the top 50% and bottom 50% would have any moral impact. e.g. two miserable peo

If you used the median then only actions which affected the utility of someone in the top 50% and bottom 50% would have any moral impact. e.g. two miserable people torturing each other or helping each other would be neither good nor bad, since the median would not change.