I’ve waged a 25-year campaign against the dash, and I want to enlist you in it. What’s wrong with the dash? A reader coming upon a punctuation mark asks two questions unconsciously: what does this mean, and what comes next? So let’s test some punctuation marks against these two questions:
A period [.] means the sentence has ended, and a new, unrelated sentence begins next.
A semicolon [;] means the clause has ended, and a new, related clause will begin.
A colon [:] means a list follows, and then the list begins; for emphasis, it might have one only item.
Ellipsis […] means something is left out, and the sentence will resume.
An open quotation mark [“] means a quotation begins, and will end with a close quotation mark.
An open parenthesis [(] means something is inserted next, and the insertion will end with a close parenthesis.
A dash [–] means, well, you don’t know, and you have no idea what comes next.
The dash is an ambiguous sign, and the reader doesn’t know what it means or what comes next. Most readers interpret a dash as an open parenthesis, and wait for the closing parenthesis. But the writer may have meant it as a pause or just used it out of habit. The reader ends up confused.
There’s one place I might think about using a dash, because there’s no other punctuation mark to cover it. I like to indicate in quotations how the speaker said it, and the dash is the only punctation mark I know to indicate a pause. You can’t use ellipsis because the reader will interpret it as something left out.
Okay, I know you love the dash, and I don’t expect to win this campaign against it. But if you want maximum clarity for your readers, avoid ambiguous signs.