Commas and dialogue.

I was reading a particular manuscript a couple of months ago, and I realized I kept changing commas to periods in dialogue. Again and again and again. No, this character can't say this in the tone of stomping away; he says it while stomping away, or he stomps away after he says it. I found the error of putting a comma after all dialogue, no matter what came after, to be far more prevalent than I thought, and I worry that I was missing this error in earlier manuscripts. To partially right my wrong, I'm sharing what I've learned, hopefully benefiting authors as much as editors.

As an author, it's a struggle to find good verbs to describe precisely how a character is saying something (although there is the argument that "said" is the only dialogue verb ever needed--I'll get into appropriate dialogue verbs another time). However, it is important that the verb can actually be applied to how someone speaks. Below are a couple examples that just don't quite work.

“No servant ever goes outside the palace,” Beatrice sniffed.
Try talking and sniffing. I end up breathing out of my nose a lot. The author is implying the character's haughty attitude. This is conveyed perfectly if the comma is replaced by a period. Beatrice talks, then sniffs, letting the reader know she's being condescending.

“It is true,” Haargen nodded. “We are just travelers seeking food and rest.”
Same story here, except it's physically impossible to nod a sentence. You nod as a gesture in addition to relaying any information more than a simple "yes." A period in place of the comma fixes it again.

So those two examples sentences were understandable. The general rule is dialogue, comma, character who is speaking, and a verb to indicate the tone of what is being said. The example verbs did provide information about tone, but they don't describe how something was said. They were body language cues written out. Below, however, are some more offensive examples.

“Then come closer, man, so that I might greet you better,” the old man waved for them to come closer.
The period here is obvious. These are two sequential thoughts that simply cannot be combined with a comma. And the old man waving doesn't tell the reader anything more about how the old man spoke. Dialogue can be followed by a period, even if the character speaking is mentioned in the next sentence. 

“That’s better,” a goofy smile on his goofy face.
This is actually missing a "he said" in there. A period won't fix it because the second half isn't a complete sentence; there's no subject. Fragments are okay at times, but here it sounds awkward, and again, a character can't goofily smile "that's better." A character can say "that's better" and then goofily smile. I changed this one to read "That's better," he said, a goofy smile on his goofy face.

The take-away: think about what follows dialogue. If the verb doesn't describe the tone of voice, then use a period.