That's because either Paul or one of the mods hellbanned him. When you're banned on Hacker News, you don't get told, because that would make you get a new account and start posting without having learnt your lesson. So instead they just auto-kill your comments to prevent other people from seeing what you're doing. (Sometimes they're polite and email you to let you know you've been banned, which is nice of them. Other times they just let you keep posting away to nobody.)
