“[The em dash] sometimes indicates an afterthought. Other times, it’s a fist pump. You might call it the bad boy, or cool girl, of punctuation. A freewheeling scofflaw. A rebel without a clause.”
There may be a better way to phrase the sentence but if it’s grammatically correct and has the right punctuation, if I’m proofreading, chances are I’ll leave it alone.
Proofreading is for the author that does not want or need any structural changes to their manuscript, nor do they need any changes at the word or sentence level. In other words, the manuscript is nearly publication-ready, or really rushed jobs where a light touch will do and “done” is better than “best.”