Q. The sentence in question is “Probability was 1.0% at first, and 2.0% at subsequent, examinations.” I did not have a comma before “examinations,” and another editor added it. Technically, she is correct, since it closes a parenthetical remark, but it reads strangely to me. This is a word-limited document and we can’t rewrite in a way that adds words. Should I leave in the second comma?

A. The problem is that “at first” is an expression that needs no continuation; the reader thinks you’re finished with that thought. (At first, probability was 1.0%.) Given that interpretation, the comma is jarring; the reader stumbles. You would be better off with “Probability was 1.0% at first examination and 2.0% subsequently.”