Stop. Now go.

The author of the book I'm currently editing consistently does a bizarre thing with em dashes.

She basically understands that one of the em's proper uses is to indicate an interruption or a sudden change of thought.

However, her execution of the em's function is literally halfhearted. For example, she writes, "These differences—as in concepts of time--need to be understood to make social interactions easier."

Why the double dash rather than the em to finish the interruption? All I can think of is that it's her way of first saying, "Stop and take note of this break," and then giving us the go-ahead to proceed to the rest of the sentence.

I have a feeling that she's never run a red light.

Yin and Yang

My favorite is the em dash. It says, "Stop! Look at me. Take notice. Something important is happening here." To my mind, it's the prima donna of punctuation, in the best sense.

And then there's em's bastard cousin, the hyphen. Half the size, twice the trouble! It intends to clarify, to help avoid confusion. "The road to Hell is paved with good intentions." I'd like to commit punctuational genocide on the hyphen.