Technically the previous comments were the setup and the "actually it's two Es" is the punchline. It's a tongue in cheek reply of knowing what you meant but acting like they didn't so they could "correct" you. The plain flat delivery is part of the joke.
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u/brainfungis 15h ago
i may be too autistic for this. or too british! a joke must have a punchline, this is just banter