Do you have mice in your pocket or tapeworm? (Sorry, Mark Twainism.) Precisely why it's ironic. Her response to him seems to be knitted brows -- a hrmph. It's also why he looks so smug when saying it. Even though I think Archer is a great character, I do think T'Pol had the upperhand on him as far as intelligence. In fact, she had the upperhand on everyone on Enterprise. I always saw Archer as a gentleman -- he offered T'Pol the blanket in Andorian Incident before he took it, let women walk into doors first, etc. But I suppose that could be another thread.