Extremely Loud and Incredibly Close Lesson Plan

What is the significance the red markings on Thomas Sr.'s letter in this section? What do they imply and how do they affect the meaning of the letter?

It has been previously established that Thomas Jr., Oskar's dad, always read with a red pen in hand to correct grammatical and factual mistakes, so readers can assume that he found this letter from his father and did the same thing. This section is one of Foer's more subtle and interesting decisions, because it gives insight into Thomas Jr.'s character in an indirect way. Many of Thomas Jr.'s marks are for grammatical mistakes, of which there are many. This is because English is Thomas Sr.'s second language, and also...