This is a rule for commas. I've always wondered how to use a comma in a quoted part. In "yes", the comma is inserted within the quoted part, so isn't "Yes", she promised possible? While a comma is separated from the beginning part of "saying ".
So for a quoted part, does a comma have to come at the end within the quoted part, and before the start?
ex)Use a comma with quoted words.
"Yes," she promised. Todd replied, saying, "I will be back this afternoon."
In American style, it would never be "Yes", she promised. It would only be "Yes," she promised.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.