This has barely anything to do with the name, the actual question is how many people would lie about their name in that situation. If nobody lied about their na

This has barely anything to do with the name, the actual question is how many people would lie about their name in that situation. If nobody lied about their name, then you would know with certainty what that person's name is, if everybody lied about their name, then you would still have no idea, except that it probably is not Mark Xu. Note that this probability is highly context dependent, the chances that your new coworker lies about his name is probably orders of magnitude smaller than that someone you just randomly met in an online chat does so.