That little bit of a friction makes all the difference. The only people who will see replies are those who are invested in the discussion. (ie, those who will r

That little bit of a friction makes all the difference. The only people who will see replies are those who are invested in the discussion. (ie, those who will return and refresh the page to see who has added what comments.) Alert replies would simply increase "engagement," and at least broadly we've seen that engagement is good for user addiction, but poor for discourse and site health.