Look deep enough into any persona and you will find something shiny within.
-- The artist (chapter 1)

Importance: This is an early indication that portraits in Killing Commendatore can reveal more about a person than their real faces. The artist is saying that he has a gift for seeing the true nature of a person within their self, and that his job, as a portrait artist, is to display that nature. There is an irony here, though, because as the novel unfolds he will not be presenting "shiny" things, but darkness and voids.

We'd lived under the same roof for years, yet I knew nothing about this woman. In the same way that people stare at the sy to see the moon every night, and yet understand nothing about it.
-- The artist (chapter 1)

Importance: The artist is describing his sudden realization that he does not know his wife, after the shock revelation that she is sleeping with someone else...