Q. If a writer presents a compound formed with a prefix that does not appear in Merriam-Webster, should it be hyphenated? Or is it OK to “create” a word by closing it up (if it doesn’t look too weird)? Of course I can’t think of any examples at the moment, but this comes up occasionally and I am often not sure how to proceed.
A. It’s not just OK—it’s necessary that editors and writers negotiate these things intelligently. Even if the compound does appear in M-W, dictionaries don’t always agree on the spelling of compounds. You should be open to your writer’s wanting it a different way. The author may be following a usage in his or her field that diverges from what’s in the dictionary. It’s why you keep a style sheet.