How do commas change the way you read?
They introduce breaks.
When reading prose, the reader should include all punctuation in his/her emphasis and tone. A comma is a break or pause in a sentence. It may mean many things; for example the sentence goes in a different direction or is moving to exemplification or is adding emphasis.
What ever the comma leads onto not only should the reader pause to reflect the comma, but also reflect any such change in the direction or purpose of the sentence in his/her tone.