Edited because I misread the description of B the first time.

If the other people's wrong interpretation is causing them harm beyond the harm that A is risking, and if the other people could be convinced of their error if A made an effort, it would be altruistic/ethical to be candid. I don't have a strong opinion on how strong the moral obligation to help others be more accurate is on A. With that caveat, A looks better in my eyes because ey figured out something other people didn't and was instrumentally ration enough to keep quiet about it, and there's no reason given to believe that B would have been candid had ey figured it out too. A is confirmed smart/rational and willing to lie about this issue, B is confirmed less smart/rational and has unknown willingness-to-lie. If <gross oversimplification> we give A 1 Status Point for epistemic rationality (figuring out the truth), 1 point for instrumental rationality (being savvy enough to lie), and -1 point for moral shadiness, ey comes out with +1 point. If we give B -1 Status Point for not figuring out the truth and no points for lying because we didn't see em face that decision, ey comes out with -1 points. </gross oversimplification>