Hacker News users are divided when it comes to notifications, many feel it adds to the notification pollution and want to stay away from any of the social network features. Although I agree on the need to control notification pollution, I think an on-demand notification service for HN like this - https://imgur.com/sCfEUO2 (mockup) is the best option to give the control to the user as Shinzo says.

Also, on-demand notification helps to spend less time on Hacker News by avoiding the need for refreshing HN pages frantically during interesting discussions.