Less so now but the whole site used to be a filter bubble of people in tech/science or with tech/science interests. It was actually a fairly positive filter though since it resulted in some very interesting content being surfaced. It still stands head and shoulders above the rest but there has certainly been some decline in recent years. In its early days, Reddit was much the same but suffered a massive decline after becoming the "front page of the internet". All "free as in beer" communities seem to follow a similar progression, those with stronger gatekeeping tend to last longer but no site can survive an overwhelming influx of new users without a proportionate increase in the ability to educate those users in the norms of the group they are joining.
How did you know that XorNot replied to your previous comment?
Notifications, addictive design and gamification are really bad practices that we should try to avoid - but the underlying drug of social media is that someone noticed and reacted to your content, and HN provides that just like Facebook or Twitter.
I think all three of you are actually hitting the nail on the head. Large headed nail I suppose ;) Take ne as an example. I could've had a really low user number on Slashdot if I had registered right away. I never actually did but I read Slashdot for many many many years.
I turn off notifications on my phone for almost any app. It's just way too annoying. I'll get to it when I get to it! I guess I'm part of that minority mentioned above but as you say I do keep coming back too. It's not black and white but we can stay on the healthy side.
If I try to find an analogy, it's the difference between sitting by the fire in the evening and chatting with other people vs. spending the entire day running around listening to and actively spreading rumors.