Hmf, I thought.

(I often think in snorts.)

What do they know from grammar? Him is the objective case of the second-person male pronoun and thus used as the object of the preposition to. Who waits modifies him and is not the tail end of a "noun clause."

Then in came a letter -- a real postal letter signed in antediluvian ink, mailed from San Antonio at the cost of an old-fashioned stamp — from Jacques Barzun, the revered emeritus professor from Columbia University who published his masterpiece, "From Dawn to Decadence," in 2000, when he was 92.