A while back I did a design for a fully distributed discussion board, kinda like Reddit but with no central host that can be controlled and must be funded by a single entity or group.
It was heavily based on the principles developed for the old USENET news network and designed to work around the problems discovered by users of that system.
I found that cryptography was a necessary component of the distributed system - it's the only clean way to solve a host of problems associated with distributed discussion boards if you want to avoid things like censorship and special interests controlling discussion.
For example allowing the moderators of a group to moderate and remove spam posts and e.g. hate speech without making that mechanism vulnerable to spoofed article cancellations is tricky. The simplest way to handle the issue was to use a public key crypto system to package moderation commands. Moderation commands to edit/delete articles are sent alongside an encrypted hash for the command. The command is only valid if the public key for the moderator decrypts the auth packet and the hash matches the command text.
Crypto is also great for things like non-repudiation and reputation systems, both of which are important for a discussion system application.
By the way, there IS a problem with HN... several, actually, depending on your view of what's desirable in a site like this. It's not terribly scalable, it's rather biased toward a particular locality's view of the world, and like many such sites everyone is effectively anonymous.
The problem with HN that a distributed system is required to address is that HN belongs to a private company that has motivations based on its own interests instead of the good of the public or promotion of free speech.
HN can be controlled, edited, is in a legal jurisdiction that allows a corrupt government to obtain control of it or otherwise interfere with it, and in general suffers from all the problems of a centralized discussion board.