Anyone can create one account for their use anytime, but if they create and use multiple accounts, they get shutdown by the site admins. HN became what you praise in part by emplacing defenses against sock puppets, an approach that’s loudly contested elsethread. That HN has remained at all nice is in part due to that “one account per person” enforcement, and the reason why is clearly stated in the guidelines:

Throwaway accounts are ok for sensitive information, but please don't create accounts routinely. HN is a community—users should have an identity that others can relate to.

I don’t mind if people keep their identity secret from the other users of the sites that verify identity. I don’t mind if people keep their identity secret from the site admins, as long as they only have one identity. Enforcing that is very hard at scale, and only works at HN due to the small size.