Mike -
Wow. Tricky situation. I had to think a lot about this. I am very close to invoking Rule 1. Or at least using it as a backup to my thought process.
Whenever someone asks me to expose a mucked hand, (which is VERY rare), if they were the one being awarded the pot, I remind them that the mucked hand becomes live and could win if it's superior. I also state that this request is not a right, but a privilege that could be taken away if abused. I then ask them if they still want me to expose that hand.
Obviously, none of that happened with this hand.
I've also never had the situation where the mucked hand became the winner.
Frankly, I've always wondered why the privilege to see a mucked hand exists at all. If it's to discourage abuse, then simply refuse if it gets abused. If it's to identify collusion, then I would think that the hand should become live regardless of who asked to see it.
Back to this original scenario.
What if before the dealer or Player 1 had a chance to say or do anything, Player 3 had simply reached in, taken his cards back and flipped them himself. Would they become live? Do "cards speak" in that situation? Regardless of Player 2's request, couldn't Player 3 say that he initially mucked, but realized it was a chop and wanted to flip them anyway? Or maybe he intended to show his cards, but they flipped mid-air and landed face down. He was gonna reach over to flip them, but Players 2 and 1 spoke up too quickly.
Additionally, is Player 1's remark a genuine request. or just a comment or afterthought inspired by Player 2's request? I think the latter.
But in regards to a ruling, based upon the scenario described and the rules as they currently exist, I would rule that Player 2's request must be acted upon before any other requests are considered. Had Player 1 said he would like to see Player 2's hand, that request is live, but is acted upon after Player 3's had is exposed.
If you want to say that Player 1's comment is a genuine request, it should at the very least, be considered as Action Out Of Turn, and therefore is ignored.
Player 1 is awarded the pot.