So is the correct answer (4) reraise and call a push? I have a hard time believing that many players will 4-bet there without a made flush.
Say 5 players in the pot, so pot is $5. You bet $5 and he raises to $10. You reraise to $30. If he pushes his last $50 on top of that he has a very big hand.
With 3 flush cards showing, flush over flush is not that uncommon. And you know 100% here you're not the one with the bigger flush.
Let's work out the odds.
3 flush cards on the board, 2 more in your hand. 52 cards in the deck, so 47 left. 13 diamonds in the deck, so 8 left. If this were headsup, the odds that the other guy would also have 2 diamonds would be (8/47) * (7/46) = 2.6%. If there are 4 others in the pot with you, then you can multiply that by 4 and have a sense of what the odds are ==> 10.4%. They're not actually quite that high, but I bet it's about 8% to 9% or so. That's not
nearly as rare as set over set on the flop, and it's common enough that I'm not willing to go bust every time I flop a flush if 5 people saw the flop.
But this guy is UTG. Unless he's crazy loose preflop, that lowers his possible # of hands that beat you by quite a bit. You can take out
[2d] and a whole bunch of other theoretically possible hands. I'm not sure how that affects the actual odds. You would have to know this guy's range of limping hands preflop, and how many of those hands contain two diamonds which are not the K9843.
Meh. I think I like option (5): reraise and then think hard if he pushes. You're not quite pot committed so you have room to fold if you want.