Bleach, if poorly spread across the film in the initial wetting of the film with bleach, can cause streaks and blemishes. In fact, Kodak states that on their web site and explicitly says that an acetic acid stop should be used in those cases. It is virtually mandatory for color paper which can suffer from the same problem.

I seem to remember that we at EK were not in favor of Citric Acid stops for color but were neutral about it for B&W.

PE