In "The Cask of Amontillado," what diction is essential to the story?

In "The Cask of Amontillado," the narrator Montresor's well-developed vocabulary and formal diction helps to give us clues about his intelligence, likely one of the sources of his immense pride, as well as his cunning. After his enemy, Fortunato, insults him, he "vowed revenge." He says,

At length I would be avenged; this was a point definitively settled—but the very definitiveness with which it was resolved, precluded the idea of risk. I must not only...

In "The Cask of Amontillado," the narrator Montresor's well-developed vocabulary and formal diction helps to give us clues about his intelligence, likely one of the sources of his immense pride, as well as his cunning. After his enemy, Fortunato, insults him, he "vowed revenge." He says,

At length I would be avenged; this was a point definitively settled—but the very definitiveness with which it was resolved, precluded the idea of risk. I must not only punish, but punish with impunity. A wrong is unredressed when retribution overtakes its redressed.

This passage clearly exhibits Montresor's elevated diction.  He could say, more conversationally, that he had definitely decided that it was time for revenge and that this revenge would have to take place without the possibility of his own guilt being discovered. If he is punished for the revenge, then it doesn't really count as revenge. Instead, he uses words like "precluded," "impunity," "retribution," and "unredressed": atypical words for the average Joe. We know that it was some insult that served as the last straw for Montresor, and because he seems so intelligent, it was perhaps an insult to his intelligence that finally pushed him over the edge. Such an insult would wound his pride and likely compel him to take action. Further, the level of intellect indicated by such language usage gives us a peek into Montresor's mind: he is clearly meticulous and attentive to detail, qualities he will need to pull off and get away with the perfect crime. Anyone with such a well-developed and precise vocabulary would have to be. Thus, his diction helps to foreshadow his eventual success in this endeavor.