The conversation between human and AI assistant.
Is it realistic that Sherlock does not know the identity of one of the characters?
Is it realistic that Sherlock, with all his intellect, doesn't know the identity of one of the characters in a case?
Well, it can depend on the context of the situation. It's possible that the character in question intentionally concealed their identity or fabricated a false one to mislead Sherlock and others involved in the case.