I'm a stickler for grammar when it comes to writing, but I've also learned along the way that fiction writing is different from other types of writing. It follows different rules. Some of those rules are fairly fixed while others are apparently subjective. In dialogue, we are allowed to make PUGS errors if it fits the character and the needs of the line. (PUGS = Punctuation, Usage, Grammar, Spelling) Some authors (I'm guilty of this one) use comma+then rather than comma+and then or semicolon+then, because it just sounds better sometimes. In the narrative, we can include things like short sentence fragments if they don't stumble the reader. In fact, I think they're great if used well. So, my question to you is: When is a mistake not a mistake? What stumbles you in fiction, and which mistakes can actually make the writing better?