The account has a history. https://news.ycombinator.com/item?id=6225716 and other comments from that account are consistent, and suggest a language other than Japanese. And bradbeattie's own link points to a table which shows that languages other than Japanese also have no direct translation for 'yes'.

Hai means neither true, yes, or no. It only means "I have heard you". This trips up many westerners.