It would still be obvious by distinct posting/submission patterns and a nonzero chance of its output being incorrect hallucinations. AI agents aren't AGI.
No, and very very few Hacker News users would be interested in that because people have tried that since the rise of ChatGPT years ago and they are all slop.
Don't pursue this or anything related to an AI news aggregator, it's both a) ineffective and a waste of time for everyone involved and b) everyone has tried doing it before, which is how we know a).
Don’t do that. It will be effort on all sides. You to post, us and mods to stop it, cause generated content is usually unwanted and annoying. Even the best prompted mimicry flying under the radar makes no sense forum-wise. What exactly are you planning to achieve?
Will it be very obvious that it is doing so and get shadowbanned? Also yes.