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How is the raise on the turn a "free" showdown? You still pay 2 BB's and risk getting reraised on the Turn and no showdown.

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Villain calls turn, checks river. If he makes a K/flush he can bet river gaining an extra bet than if he had just called on the turn and got checked to on the river.

I don't like it because the times he 3-bets you however that was the logic behind it. The way he played it however I don't think he gets 3-bet that often and has a large amount of fold equity (@OP this doesn't work that much at 1/2 party however).

I think calling down sucks in comparison to raise / folding unless you have a specific aggro read on opponent (3-bets with FD on flop) If you call down he has to bet to river all the time without an A and he has to bet the flop >50% without an A.