Plot hole: In the scene where Westley is tortured to extremity, he screams, and upon hearing him scream, Inigo is instantly able to identify Westley and that he is in love with someone about to marry. You could say Fezzik told him, but how did Fezzik know? For all they knew, he was just a pirate after a prize.
Suggested correction: He doesn't instantly identify Westley; he identifies the sound of ultimate suffering. He surmises that it must be Westley because he can't think of anyone else who would have cause for ultimate suffering. By now the news would have spread that Humperdink's men apprehended a pirate claiming to be Buttercup's true love. Inigo was simply putting two and two together.
Other mistake: When a disguised Westley see Vezzini holding a blindfolded Buttercup hostage, Vezzini is sitting down with a blanket, some food, two goblets and a bottle of wine. There's no way that Vezzini should have these as he wasn't carrying anything on him when he got out of the boat and Fezzik took everyone up the Cliffs of Insanity.
