If the Moating player doesn't get to see revealed cards, then here is an accountability issue that could arise in a 2 player game:
A: Plays Ambassador
B: Reveals a Moat from their hand
A: Reveals a Patron from their hand and gets +1 Coffers (and chooses not to return the Patron to the supply)
If B doesn't get to see the revealed Patron card, then there is nothing to stop A from always conveniently finding that they have a Patron in their hand when their Ambassador is Moated.
I was aware of the accountability issue, meaning this would go against the intent of the rules, and I never play this way (I let revealed cards be revealed for blocked attacks), but I was wondering if there was actually anything that specifically said that revealing isn't considered an effect of an attack.
I suppose the answer could come through the fact that revealing is effecting the player revealing it, even if it's not explicitly stated. The act of revealing could be beneficial to the opponent, but isn't made to be that way.