Nick interrupts the plot/narrative flow in order to provide commentary. how do you interpret his observations? is this a necessary interruption? why or why not?

This one is actually a good question. Well first, this is from the great gatsby. Fitzgerald was trying to give a balance view in the beginning of who the great gatsby was. And even the author, he lived a wonderful life that is why he related that into Caraway's character, having the same background as him.