It's been their policy for a while now. Source is dang himself: https://news.ycombinator.com/item?id=49078714

> Your posts are getting killed because our software classified the text as genai. That's not allowed on HN - see https://news.ycombinator.com/newsguidelines.html#generated and https://news.ycombinator.com/item?id=47340079.

> Can you write by hand any text that you plan to post to HN? Here's an important tip we send to users about this:

> Write any text that you post to HN by hand. Don't use an LLM to generate any of it (not even a tiny bit, including to edit or spruce it up). Reason: the community is super fussy about this right now, and LLM language has a certain quality that is generating quite some backlash when it appears on HN itself. This is a big dividing line at present!