You mentioned abuse of the em dash in your response to summer's question. Can I ask you to elaborate on that? I won't lie. I utilize the em dash when I feel it's appropriate, but I do see instances where writers use them in every frickin paragraph, disrupting sentences unnecessarily by inserting sentences within them. That's overuse, of course. But what's the perspective from an editor? What's too much? Obviously it varies from person to person, but in general?
The em dash, once people learn about it, soon becomes their favorite method of punctuation. Which is fine, provided it is used well, and not like it’s being aimed at the text like a machete, hacking it up into illegible choppy segments.
My general rule of thumb is that the em dash is fine to use in place of commas to make reading tone* easier—provided the information is interesting and vital—and not just inane rambling. Often times it is not the use of the em dash that is the problem, but the inclusion of unnecessary information to the text.
It can also be used instead of parenthesis (which can often seem rather formal in fiction writing), to add more info. The em dash is a bit more flashy than parenthesis however, which is accepted to be a bit more subtle. So if you want to draw emphasis to something, use them em dash, if subtlety is your aim, use parenthesis. Sort of like the difference between a shout and a whisper.
And of course it can also be used in place of a colon—to add emphasis to a final line.
Generally speaking, so long as you’re not using more than two per line, you’re fine. But again, it depends on how it is being used. I’ve seen it used twice in one line in the same way you would use a colon, in which case that shit needs to be a whole new sentence of its own.
So there’s no harm in using one or two every paragraph. It’s just learning when to use them, and when it’s okay to trust in the oxford comma.
Does that help? It’s late and I’m sort of running out of steam but I hope that helps clarify this for some people.
*the overuse of commas can be just as equally annoying, and can often create a sort of breathless quality to the narrative. The em dash in this instance allows the reader to draw mental breath, absorb some vital tidbit, then plunge on with the rest of the narrative.