And in my experience at least, I have seen and participated in many, many valuable, interesting and enlightening discussions here on HN, and see little evidence

And in my experience at least, I have seen and participated in many, many valuable, interesting and enlightening discussions here on HN, and see little evidence that it is going away from that. True, badly made arguments are treated rather harshly, but that is more of an advantage than a disadvantage for a discussion forum.