Ok so this is the point to where we differ. I read Art 4 as follows in this case: You are a natural person who can be indirectly identified by refering to an online identifier (your username). This identifier is therefore personal data. HN also has your IP while and a mail address. So they have a much stronger link. Maybe they also have information about the sites you visited and the comments you made. If one would read all of this, maybe this someone would have a good profile about you and could identify you.