Because they are feeding titles into classification function and based on what they don't like which they've established before, they kill the post before anyone can see it. NH is criminal and they'll never release the source code because they will be punished for what they're doing.

Curation and moderation aren't "criminal," and HN doesn't release their fork of Arc Forums because it contains business code for YC that would be a hassle to get rid of, but the original is open source. People come here because they want that high barrier to entry for content. If you just want a firehose of random shit go to Reddit.