alt Hacker NewsAI-edited or -generated comments are disallowed by HN guidelines: https://news.ycombinator.com/newsguidelines.html#generated. I don't think any such restriction exists for submissions themselves, so that's my guess as to why the comment but not the submission has been flagged to death.
No restriction for the submission itself, unless it’s something like an Ask/Tell/Show HN, in which the content goes directly on the post (and will get flagged if AI-generated/assisted)