Ask HN: How can HN allow login without an email and not be full of bots?

When I created an account today, I was really impressed by the fact that I didn't have to input an email before I started commenting. It almost seems unprecedented, especially given this is a site that caters to hackers. How can Hacker News have a login flow like this and not show any huge signs of abuse?

I tried searching for an article on it, but found nothing. In terms of general "login without email", the best I could find was a UX discussion. Anyone have any leads?