I'm not always a fan of using proper grammah in fiction, partially because i don't remember (or, if pressed on the topic, don't care) that much about it. Even though i learned it all in uh, grammar school (for those outside of the USA, "Grammar" or "Elementary" School is generally attended prior to age 14 or so), my sense of grammar is probably more intuitive than thoughtful; if it sounds and looks right to me, I will use it. If "grammar nazis" (no one here fits this bill) criticize me, I will usually respond in one of 3 ways: a sincere "thanks for pointing that out," a sarcastic "thanks for pointing that out," (go ahead, you figure out which one I really mean), or a sincere/sarcastic explanation - depending on my mood - which essentially boils down to "yes, I meant to do that, and here is why."
The one use of the comma, oxford or otherwise, which i don't remember seeing in previous posts, is to control pace. The comma slows the reader down, making him or her pay just a little more attention to what has been written. A writer can use it, especially after a long segment of fast action or dialogue, to slow the story down, make it more introspective, and let the reader's brain take over while their emotions and heart rate get back to normal. In these cases, a deliberate (little pun there) use of the comma, even if used incorrectly, is a useful writing tool.
BTW, on a less serious note, I deliberately used a number of the different types of punctuation in the first paragraph. Feel free to point out any incorrect usages. My response will be "thanks for pointing that out."
