FWIW, I think, in the original scenario, because Jester does not say that it reveals the card, the reaction could not be triggered. You can see the top card of your discard, so you don't need to "reveal" the card to gain a copy.
If there is a rulebook somewhere, that I am unaware of (or if you wanted to create the rule about discarding for this card), that says a card is revealed when it is discarded, then it would change the result. You would then be able to trigger the reaction, but since the reveal is a result of the discard, the copy should still happen, because the discard happens first, and can't be undone.
(unless you added a Trader-like condition of "when you would discard this card")