> Once the room becomes an active participant and manipulator it becomes what is now a modern "social networking" site, and should be regarded as poison.

Hacker News is one of the most aggressively moderated forums you'll ever come across, the room is very much an active participant and always has been.

And the entire purpose of the karma system (particularly the censorship of downvoted items) is to suggest and promote some content over others. That HN doesn't use machine learning is just a quibble about complexity.