Offer a Duel states:

F Commit 1 foundation: Each player chooses 1 card from their hand and places it face down in front of them. Each player reveals the chosen card....

Just Kidding states:

E Commit: Both players reveal 1 card from their hand. If the revealed cards are the same card type, this attack gets +3 speed...

My question is, with Just Kidding. How is it decided who reveals first? Is there anything stopping one person from waiting for the other person to reveal first thus controlling (in most situations) whether a speed boost is granted or not?

both players place the card to be revealed face down on the table.

Both players then reveal their cards simultaneously. Because the card has been selected prior to being revealed there is no shenangins.

OK, to be clear, even though Just Kidding does not specify the revealing process in the same manner that Offer A Duel does; that is now the proper way to play this sort of ability. Correct?

ROTBI said:

Always was. Offer a duel just happened to be excessively verbose.

Thanks for the reply, sir. Unless I overlooked it, the AGR didn't mention this process, so I've always been under the assumption Offer a Duel was the only card that worked that way.

ROTBI said:

If a card says "both players reveal" the process is to do so simultaneously.

To prevent cheaterie <yes I made that word up> and shenanigans, the method proposed by offer a duel is the fairest way to do it. I mean you don't have to put them face down on the table first, but you have to indicate which card you have selected prior to revealing said card, so both players know that you're not just doing what you are concerned that a less then honourable player might attempt to do.

There are cards where it declares that one player reveals, and then another player reveals, in that case, it's ordered as per the card text.