A couple of examples of where I haven't used but have needed commas are:
“They’re almost done, father!” The girl replied, spinning on her heel over to the stove and checking the cooking food with a wooden fork. from Chapter 1: The Girl from Two Worlds
“Oh,” Irene paused to snap the weakened vine in half, pushing the rest of the way through the underbrush, “since, um, since Arminius and I aren’t… together, we can’t together, but I would love to have you stay with me.” from Chapter 6, Influence
My editor also provided a link of humorous sentences that illustrate the commas' power: http://www.buzzfeed.com/daves4/commas-are-the-most-important#.gokBAPWWX
Let this be a lesson to all creative individuals. Always seek at least one other opinion about your work and befriend the comma.