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No, it's for value whenever his hand is best. If he checks most better hands will bet but some worse hands that will call a bet will check through if given the chance. IF UTG missed a draw he'll likely give up on the river as well and then hero misses value from MP if he doesn't bet it.

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I still can't see ANY worse hand calling this river when Hero pops out of the blue on a blank and donks.

Are you hoping MP has a 7, a 2, pocket 4s?
I don't get what value Hero's missing.

I think you've got a much better chance of a villian betting a worse hand in this situation than someone calling with a worse one.

I'm obviously completely missing something here...