Pointing out a bug in the code is not a comment on the programmer. Programs have bugs! Humans make mistakes. Commenting on a review with 'you made a mistake' is

Pointing out a bug in the code is not a comment on the programmer. Programs have bugs! Humans make mistakes. Commenting on a review with 'you made a mistake' is needlessly confrontational. but the alternative is wasteful: bending over backward to avoid even suggesting that the code might have a bug. If the reviewee's ego is based on never making mistakes, then the review will hurt their feelings regardless of how the comments are phrased.