"Why so dull?" --Babbalanja in Melville's Mardi: And a Voyage Thither
"Ah, why so dull?" --I. F. [Imaginary Friend] in the September 1851 installment of Scenes Beyond the Western Border; and Scenes and Adventures in the Army
More accusations of dullness, in dialogue:
"How very dull you are." --deleted in revision of Melville's The Lightning-Rod Man (appears in Putnam's magazine but not The Piazza Tales.
I. F. "Talk of dullness! and you are half asleep, and have just made a pun that is malicious premeditated dullness." --September 1851 Scenes Beyond the Western Border; and Scenes and Adventures in the Army