There's two points being made here and they're not all that clearly distinguished. First, excursions, where a new thought is interpolated into a sentence befor

There's two points being made here and they're not all that clearly distinguished. First, excursions, where a new thought is interpolated into a sentence before the previous one is complete, can be tiring. Second, people use em dashes where other punctuation would be more appropriate—the article illustrates this nicely, where lots of em dashes are used that would better be commas or semicolons. Em dashes are the most emphatic punctuation for communicating excursions, so the two points are related. Indeed, em dashes should be used sparingly, as exclamation marks are, since they are visually distracting. Chicago suggests that no paragraph should contain more than two em dashes, and most should not contain that many. By my reckoning, Noreen Malone packed 14 em dashes into each of two paragraphs in her article. But the fairly mechanical task of turning dashes into other punctuation doesn't tackle the point about excessively excursive writing. And here I don't agree that they are the enemy of "truly efficient writing". Excursions can be a sign of mental disorganisation in the writer, one who isn't writing with clear purpose, but they can also be the sign of a successful reworking of complex material, to present it in the most digestible manner. I don't think that "excursions bad" is useful advice, rather I suggest "check that excursions are of clear value". I have three excursions in this comment, and I think all pass this "clear value" test; as an exercise, you can check if you agree with me. There's an em dash too.