This is well known in psychology, a combination of the mere exposure effect as well as Baader–Meinhof phenomenon (frequency illusion).

The latter makes sure you notice again something you've already seen. The former makes you associate that thing to being good, by its mere presence.

And as to your first sentence, HN will put newer comments at the top of the comments list in order to get people to see and engage with them (as I've done) :).