Hacker news has a shadow banning problem. Unpopular opinions are downvoted into oblivion. Then your posts start going into the void.
Their house, their rules, and IMHO the good outweighs the bad... but make no mistake, calling HN a "marketplace of ideas" is inappropriate.
But it's mistaken to say HN is a free marketplace of ideas.
I could give some substantive points in support of this statement, but it's an old conversation and I've gotten in trouble for the ways I've expressed it in the past.