Ask HN: Whether there is LLM or other strong NLP behind Hacker News?

I found that if your post is a LLM generated content, it will be auto-hide.

And I heard long time ago for same product you could not share in Show HN for multiple times.

What is the mechanism behind? Is Hacker News using LLM to judge each post or retrieve the product name and deduplicate in Show HN?