it does not mean it was positive, people do a lot of things since the dawn of time (slavery for example).

the fact that something was used for a long time means only that it was used for a long time, and everything else is up for interpretation.

Most of its usage is on platforms where engagement is how they make money. Any kind of engagement. Considering flamewars, nitpicking and arguments are goldmines that capture user attention, it's in the platform's best interest to draw attention to threads via notifications.

Is this the right thing for HN? I don't know. But they've decided it's worth the trade off, I think.