At one point, Fortunato repeats a grotesque gesture, allegedly a sign of the mason brotherhood. He asks Montresor if he understands, which Montresor does not. Fortunato concludes that Montresor is not a mason. But Montresor claims that he is. This may not be a direct insult, but Fortunato seems indignant and can not believe that Montresor is from the same brotherhood as he claims to be. Fortunato repeats this gesture so this could be considered a second instance of insult:
He laughed and threw the bottle upward with a gesticulation I did not understand.
I looked at him in surprised. He repeated the movement--a grotesque one.
Fortunato insults Luchesi, calling him an ignoramus; this is the most obvious insult from Fortunato. But while Fortunato and Montresor are in the catacombs, Fortunato does not really insult Montresor in any overt way. The only other possible insult is that Fortunato notes that he does not remember Montresor's coat of arms. This seems like a stretch to call it an insult, but if family pride was paramount in this social circle, knowing each others' coat of arms might have been assumed. The compelling and confounding thing about this story is that the reader doesn't really know how Fortunato has wronged Montresor in the first place. Each example of an insult, above, is a bit of a stretch. While Fortunato does seem stubborn, proud, and drunk, he does not overtly insult Montresor (with the possible exception of the mason remark) and that's what makes the story provoke so many questions, such as: "Did Fortunato deserve such a fate?" and "Was Montresor guilty and/or did he feel guilty in any way?"