"Enough, the cough is a mere nothing; it will not kill me. I shall not die of a cough."
There were no attendants at home; they had absoded to make merry in honor of the time. I had told them that I should not return until the morning and had given them explicit orders not to stir from the house. These orders were sufficient, I well knew, to ensure their immediate disappearance, one and all, as soon as my back was turned.
The reader knows that Fortunato looks ridiculous, yet Montresor complement his looks out of all things.
I must not only punish, but punish with impunity.
Montresor knows he will die, just not of a cough, it is ironic because of how true the statement is, but Fortunato doesn't understand the truth in his statement.
He had a weak point-this Fortunato.
While one expects the attendants to listen, especially to such strict orders, they did the opposite, and Montresor knew that they would and that this would happen.
I will not impose upon your good nature. I perceive you have an engagement.
This foreshadows the drastic measures he will take to get revenge because to get away with it he can't let Fortunato tell people and killing him will keep him from that.
This foreshadows how the wine will be used to bait Fortunato because Montresor points it out as a weak point of Fortunato.
He prided himself on his connoisseurship in wine.
Montresor confirming that Fortunato has no plans foreshadows that Montresor will get away with his crimes because if something happens to Fortunato, no one will look for him since he isn't expected anywhere.