Basically, my question is this: when I discard cards for Militia, do the other players have the right to see all the cards that I discard, or just the card that ends up on top of my discard pile.
I believe this comes down to the question whether the cards are discarded simultaneously or one after the other. There are contradicting sources on this. The DominionStartegy Wiki page states
When attacked by Militia, you do not have to let players see all the cards you discard, just the one you leave on top of your discard pile.
However, the book Complete Rules for Dominion and All Its Expansions v.7.0 on page 40 under "Discard down to x cards in hand" (explicitly including Militia) states
Discard cards from your hand, one at a time, until you have x cards in your hand.
Are there some official words from Donald X. Vaccarino?