This paper examines the authorship of postpublication criticisms in the scientific literature, with a focus on gender differences. Bibliometrics from journals in the natural and social sciences show that comments that criticize or correct a published study are 20% to 40% less likely than regular papers to have a female author. In preprints in the life sciences, prior to peer review, women are missing by 20% to 40% in failed replications compared to regular papers, but they are not missing in successful replications. In an experiment, I then find large gender differences in willingness to point out and penalize a mistake in someone's work.