Because a ranges become *extremely* narrow when we face a river 3!, and in these games, it is the nuts VERY close to 100% of the time. The nuts make perfect sense here (he might call suited Qs as low as Q7s to a small blind steal, and every single postflop street makes perfect sense with Qxss), and anyone who thinks he might be bluffing here should be sectioned.

I suppose there's a question of if he's so unconcerned about the backdoored flush that he's trying to make up value with, eg, a flopped set that missed a x/r, but 1) That only adds 6 combos of sets that are pretty heavily discounted, 2) if he's doing this with anything short of the nuts, then that adds several combos of flushes, 3) I think it's way too thin to expect him to do this with KQ/AQ. Also, point #4: People in these games don't value raise rivers with anything short of the effective nuts.

This guy's river 3b is totally unbalanced, so just EBF, my friend. Exploit by folding.

Perfectly put. Neither of these decisions is close. Regarding the river, people seem to think that one of these things has a non-negligible chance of being true:

1. He is 3betting the river for value with a set or worse.
2. He is 3betting with JT that inexplicably called the flop bet and we chop.
3. He is 3bet-bluffing with... something?

A good player is, for certain, not doing 1. Regarding 3, think back to the last time you saw a live 3-bet river bluff in a 1/2 game. 2 is possible except for the part where villain peels the flop with 2 undercards and a BD straight draw.

EDIT: And just to be clear, 1 + 3 + 50% of 2 have to add up to a third of the time. A third of the time! Not even close.

I'm confused. You have the second nut flush? Or JTo? Without the flush I think it's a fold. Likely some Qx flush made it.