> Does anyone know if GDPR (or similar law in the future) will actually force HN and other sites that don't have this feature, to remove accounts, at least EU ones, upon request?
As far as I know, the GDPR is more of a clarification (along with some explicit guidelines for fines), than it is new legislation - so hn and similar sites would already be in breach, if they didn't allow the deletion of all profile data. I'm not certain that having to email someone at hn to do it, would be in breach of current data protection regulation. It may be that not clearly stating: "to get a record of all data hn has stored on you, make correction or delete all data - please email (...)" will be in breach of GDPR.
But afaik hn does no business in the EU - so it's not clear what sanctions would be applicable.
It's different for companies that does business in the EU / EEC.