I wonder if she's actually in love with Walter, or not,'" Seth mused optimistically, uncorking a final bottle. 'Physically, I mean.
-- Seth ("Good Neighbors" paragraph 17)

Importance: Seth''s words make it very clear that the state of Patty and Walter's marriage is no secret.

Oh Walter: did he know that the most intriguing thing about him, in the months when Patty was getting to know him, was that he was Richard Katz's friend? Did he notice how, every time Patty saw him, she contrived to find nonchalant ways to lead the conversation around the Richard? Did he have any suspicion, that first night, when she agreed to let him call her, that she was thinking of Richard?
-- Narrator (Patty) (Chapter 2: Best Friends paragraph 320)

Importance: This quote highlight's Patty's sexual motivations even after getting to know Walter. Richard seems to have always been Patty's priority.

Time passed in a peculiar manner which the autobiographer, with her now rather abundant experience of murdered...
-- Narrator (Patty) (Chapter 2: Best Friends paragraph 832)