What is unusual about the way the narrator tells his story? How does he represent Porphyria's actions and emotions in the poem "Porphyria's Lover"?

The narrator's presentation of Porphyria's feelings and actions is unusual because he retains the same tone even after he's described the way he's murdered her.  It happens so quickly, and he speaks of it so lovingly that we could almost miss that it even happens.  The narrator rejoices that Porphyria loves him, and he wants to preserve this perfect moment.  After he strangles her with her own hair, she opens up her eyes and says...

The narrator's presentation of Porphyria's feelings and actions is unusual because he retains the same tone even after he's described the way he's murdered her.  It happens so quickly, and he speaks of it so lovingly that we could almost miss that it even happens.  The narrator rejoices that Porphyria loves him, and he wants to preserve this perfect moment.  After he strangles her with her own hair, she opens up her eyes and says that they "Laughed [...] without a stain."  He describes her cheek as "Blush[ing] bright beneath [his] burning kiss," as though she could still flush or feel joy or pain.  He describes her head as "rosy," like she could feel happy or "glad" that her will has been honored: that they can now be together forever.  In short, the narrator seems to have no sense of the fact that by attempting to preserve the perfect moment, the perfect feeling, he has destroyed it.  This is dramatic irony: we realize something that the narrator has not.  This presentation of Porphyria's feelings, then, is quite tension-filled and off-putting because we realize that the narrator has ruined his love while he continues to believe that he has saved it.