How should one handle the interaction between these cards (assume the same player, Nnenn, controls both) w.r.t. keeping the top card of the library revealed (per Courser of Kruphix) while resolving Dig Through Time?

More specifically, after resolution of Dig Through Time, will other players know whether the previously revealed top card is now in the player's hand?

My intuition is no, because the choices are being made in a hidden zone (library), and so the procedure would be: the top card remains revealed while Nnenn looks at the top 7 (first sentence of DTT), then the top card is turned face down while Nnenn makes choices, placing 2 in hand, and rest on bottom of library (second sentence of DTT).

Your intuition is correct. Nnenn's opponent is not entitled to know whether the top card was one of the cards put into Nnenn's hand or whether it was put onto the bottom. The fact that the Courser was revealing the top card of Nnenn's library doesn't matter.