Yes, but HN is a zero-distraction distraction: It's a workplace procrastination tool that doesn't let the user veer too far from their work. You can see this in the anti-procrast settings and the lack of any advertising here (both of which are very nice features I use regularly). If HN had notifications it'd lead on a slippery slope to HN being a social network instead of a news aggregator, and I don't think anybody wants that.