Then they would not out their identity by claiming to have worked with the author. That piece of information alone whittles their identity down to maybe 100 people. Out of 100 adjacent academics how many post on HN, with this style, and this specific level of knowledge in that specific subfield? They may as well have just made the account their irl name. Anonymity is not a realistic goal. Assuming a realistic poster means it's reasonable to suspect their earnestness.