One of the strong indicators is the use of italics in the post. Many users will ignore formatting within their posts. I am confident this user has used italic

One of the strong indicators is the use of italics in the post. Many users will ignore formatting within their posts. I am confident this user has used italic formatting before for emphasis and has done it often within their HN posts. It also indicates a comfort level within HN which means they have likely posted frequently. (At least one a month)