I just remembered something else that copy-editors do at newspapers: they write cutlines, that is, the captions to pictures. (In newspaper jargon, a picture is a cut.) Here’s one from the New York Times:
Two images of the same cuttlefish, taken fewer than two seconds apart, showing how quickly it can change color.
The copy-editor (or whoever wrote that cutline, the Times having abolished its copy desk) is to be commended for trying to get the distinction between less and fewer right, but this time she or he failed.
We use less to express amount and fewer to express number. The important concept in this cutline is not the number of seconds involved, but the amount of time.