I don't believe this example is either one of irony or foreshadowing. Montresor is leading Fortunato a long distance in the darkness. One of Montresor's many problem with getting his intended victim to the niche where he plans to chain him to the wall is that Fortunato might become suspicious and balk at continuing. Why should Montresor have stored a huge cask of wine at such a great distance from the foot of the stairway? Instead of encouraging Fortunato to continue to accompany him, Montresor does just the opposite: he urges him to turn back. The effect of his is not exactly that of reverse psychology. Rather, it eases any suspicion Fortunato might be developing. If Montresor had any sinister purpose in leading him to a certain destination, why would he keep urging him to forget about the Amontillado and go back the way they came? Montresor has nothing to lose. He is armed with a rapier, while Fortunato is drunk and unarmed. Montresor can kill him any time he wants, but he would prefer to get him to that niche with the chains attached tothe granite wall. Otherwise, he might be forced to drag a dead body for a long distance and also lose the pleasure of having Fortunato understand that Montresor is exacting revenge for a thousand injuries and beg for mercy.