Hyphens, En Dashes, Em Dashes

Q. Forgive me for what might be an obvious and maybe annoying question, but what do you recommend when your advice seems to differ from M-W Collegiate when it comes to hyphenation of prefixes?

A. Here at CMOS we follow our own hyphenation advice. That’s more or less the point of coming up with it. Merriam-Webster’s is the backup dictionary we use when CMOS doesn’t state a specific style.