Back in December at Language Log, the urbane Mark Liberman commented on a text distorted by a ham-fisted attempt to convert British English to American, saying, "God save us from such copy editors." That provoked a spirited defense of copy editors in the comments by the doughty Dick Margulis. They leave me with an impulse to explain to my civilian readers what goes on in copy editing.(Colleagues, you can lean back on your oars for a while.)

Think of a copy editor as a parent trying to clean up a teenager's room. You open the door and, God above, there are discarded articles of clothing on every surface. You start to dig in and discover dirty plates, some with unconsumed food on them; notes and uncompleted homework assignments; still more malodorous articles of clothing, along with the unspeakable sheets; and, under the bed, dust bunnies the size of tumbleweeds.

The basic function the copy editor performs, in all circumstances, is cleanup. We regularize the punctuation, correct the misspellings and typos, fix lapses in grammar and usage, untangle knotted syntax, and the like. And in public perception, that's about it; we are essentially proofreaders, and we can keep our opinions about the prose to ourselves. (Some writers share that perception.)

But copy editors who are allowed to edit do more. They are not merely hauling the teenager's dirty clothes down to the laundry room; they are putting the room to rights.

Proper copy editing includes examining the focus, dredging the main point up from the tenth paragraph to make it more prominent. Proper copy editing addresses the language: rooting out cliches, substituting an ordinary term for jargon when it would serve the reader better, altering infelicitous wording. Proper copy editing prunes, deleting the irrelevant, tightening the language. Proper copy editing raises serious questions, including the kind that can identify plagiarism, fabrication, and libel.

Got that? Now here is where Professor Liberman and Mr. Margulis are both right.

There are indeed copy editors who exercise poor judgment. I know that some are fettered by clients or publications who enforce idiotic preferences, but there are some who just bear down too hard. The inherent hazard for the copy editor is the tendency to see everything as a one or a zero, right or wrong. There are copy editors for whom the Associated Press Stylebook is not a collection of guidelines of varying reliability, but Deuteronomy and Leviticus and the Uniform Code of Military Justice rolled into one. Some of them hold fast to the schoolroom superstitions and zombie rules they learned early on and never examined.

These are the copy editors whom Mark Liberman and Geoffrey Pullum rail against. It is not that they make mistakes; all of us do that. These are copy editors who make bad judgments on principle. And I cannot defend them.

But I can quote Mr. Margulis on copy editing: "Typically they do what publishers ask them to do. Publishers have style guides, most of which are crotchety and old and full of zombie rules and are sacrosanct because they were written by someone long gone and long forgotten but revered nonetheless. Managing editors are bureaucratic functionaries responsible for moving the project along, not necessarily skilled editors or people knowledgeable about linguistic subtleties, and they require the copyeditors they assign to follow the style guide as written, not quibble about zombie rules. Publishers see copyediting as a low-level mechanical function, and they don't pay well for it, so there really is not time available for copyeditors to give serious consideration to doing more than they're being paid to do. However, what they're paid to do is mark up the manuscript to note everything questionable and let the author and the managing editor make the final call on which changes to make and which to stet. Blame the publisher, not the poor copyeditor."

And further, commenting on Geoffrey Nunberg's post " 'The data are': How fetishism makes us stupid": "Most raw manuscripts are cesspools. The vast majority of authors—people with knowledge and authority who have a story to tell or a theory to espouse—are not writers. They may have passed high school English, but that doesn't mean they can string words together into grammatical sentences (by anyone's definition of grammatical). In academic, scientific, and medical journals, a great many articles are submitted by people who do not have English as their first language, and even the authors whose first language is English don't necessarily have a great command of it. So while it's true that a good writer may occasionally take offense at what an overzealous copyeditor does to ruin a perfectly good sentence, most of the time copyeditors—even the bottom half—are performing a valuable service, turning semi-random strings of characters into at least halfway intelligible English prose. And most of them are doing it for pay that I daresay no college professor would deign to work for."

The blunt truth is that most people, and that can include many academics, are not very good writers. Their prose needs the basic cleaning up, but it also needs the clarification, the sharpening and pruning. The sad truth is that many professional writers are not particularly good at it either, and I can speak from the experience of one who has dealt with the prose of hundreds of professional journalists. As my former colleague Rafael Alvarez once said after a stint on the metro desk, "Reading other people's raw copy is like looking at your grandmother naked."

So, dear reader, take this home with you, There are indeed overzealous or ill-informed copy editors who mar texts through defective judgment. But to the degree that copy editors are still engaged, and allowed to practice their craft, they are doing you a valuable but anonymous service.