One can infer that Montresor is a wealthy man, judging by his many servants and large palazzo. He also seems well educated, speaking eloquently and using Latin and French phrases in his speech. While not as knowledgeable in wine as Fortunato, he knows enough to feel at ease discussing its virtues. His family is clearly an established name, judging from the catacombs filled with generations of Montresors. He also speaks at length about his coat of arms, suggesting that he comes from a well-respected clan. He himself seems well-known in the community, and he is familiar enough for Fortunato to follow him without question.
There is much evidence suggesting that Montresor is unreliable. He reveals in the first sentence that he intends to have revenge from Fortunato. Yet he never explains why, stating only "a thousand injuries" and "insult". If the narrator cannot even reveal why he is motivated to kill, he is untrustworthy. He tells the story to an unidentified "you, who so well know the nature of my soul,’’ but this "you" does not appear to respond in any way as Montresor delivers a long monologue. Is he addressing a random audience? A specific friend? Since we can't be sure to whom he is speaking, we can't be sure he is telling the truth.
The most striking thing about Montresor's voice is his outright confidence and determination. He tells the story from beginning to end with no diversions, no explanations, and no emotions. This sense of detachment is in itself unreliable. Of course, he is relating an event which occurred over 50 years ago, and we cannot be sure if he is correctly recalling his state of mind. In fact, we have no insight into his current state of mind, for he gives no reason as to why he might be telling this story now. If he is celebrating the anniversary of gaining his revenge, or if he feels guilty about his crime, he does not speak of it directly, and his language does not reveal it.
By presenting the story in the first person, Poe avoids responsibility for any interpretation of the action. Montresor is in control, deciding what to tell and what to leave out. As an audience, we are left at the mercy of this clearly unhinged character. A third-person narrator would have presented a more balanced story. An objective narrator telling a terrible story objectively might be frightening, but even more frightening is a man telling without emotion the story of his own terrible crime.