The interpretation and placement of commas, quotations, periods, etc. truly depends on context. Taking again the dual nature into account, it can be seen as a dialogue between two selves. "The one who was, and the one who comes."
Greek Οὐκ εἰμί, "I am not."
Greek Ὁ προφήτης εἶ σύ (Ho prophētēs ei sy) translates to "You are the prophet" in English.
Greek Καὶ ἀπεκρίθη oὔ. And he answered not. Οὔ is a particle of negation. This form is found around 700 times, the vast majority of times it negates -- "not". For the text to have only "No" as dialogue doesn't fit with the overall linguistic and narrative patterns found in the NT. This would be the shortest spoken dialogue/answer/word/reply in the entire New Testament otherwise.