This may seem odd that I, as a copy editor, whose premiere style guide is 16CMS, can take issue with any rule therein. However, as we find in other applications in life, what sounds great in theory needs some tweaking in practice.
Serial Comma. Per 16CMS 6.18. Granted there are grammar posts that say this construction is falling out of use and I say, yes! First, when both 16CMS and Web11 seek clean and uncluttered writing, unhindered by useless or repetitive words, with a spare hyphenation style, why push a duplicative final comma before and as in red, white, and blue? After all, the commas which separate a string of same-category adjectives (not cumulative adjectives) are just placeholders where an and could be instead. Example: Red, white, and blue could just as well be written as Red and white and blue (which is one example of a rhetorical device). In my own writing, I refuse to use the serial comma as illustrated above. Now I do use a serial comma variation, also found in 16CMS 6.18, that helps with clarity. Example: We are having bacon and eggs, toast and jam, pancakes and syrup, and fresh fruit compote for breakfast. In the previous sentence, the final comma helps keep a pair of food items together as if one single offering. The comma in that instance adds clarity. It is needed.
M-dash and dialogue. Per 16CMS 6.84: If the break belongs to the surrounding sentence rather than to the quoted material, the em dashes must appear outside the quotation marks. "Someday he's going to hit one of those long shots, and"—his voice turned huffy—"I won't be there to see it." Technically the only problem I have with this construction (and there are two others also within 16CMS 6.84) is how this works on an e-reader. There are no spaces around the M-dashes as used above, which is as it should be when using any of the dashes: the more common hyphen, the N-dash and this M-dash. But because of the "no spaces" construction, it makes for messy highlighting on an e-reader or just for abnormal line breaks. It must really create strange screen loads on a smaller device like a cell phone. For this reason alone, I prefer this arrangement: "Someday he's going to hit one of those long shots, and—" his voice turned huffy "—I won't be there to see it."
Ellipsis or Suspension Points. Per 16CMS 13.48, nonbreaking spaces are to separate each of the periods along with a space preceding and after the three spaced periods. I refuse to do this in my own work. I prefer the keystroke [Ctrl+Alt+(period key)] function which is streamlined and keeps the three periods together, and I also delete the fore and aft spaces as well, making the ellipsis character work like those of the dash family: with no separating spaces. It remains clear and there is no ambiguity.
Whether you stick strictly with 16CMS or deviate, be prepared to defend your choice. As we all know, our Americanized English language has tons of exceptions to most of its rules. Watch out for those as well.
Denise Barker, author + blogger + copy editor