There are definitely ideas that are not allowed here.
I think so long as you follow guidelines generally and don’t outright attack individuals then you’re mainly ok. The community might downvote your idea to invisible but that doesn’t mean it wasn’t allowed - just that not enough people thought it was good. That’s fair.
This might be a nitpick, but this depends on your POV of who's allowing/disallowing content.
HN itself allows a lot of comments that the collective HN community does not allow -- by downvoting them into invisibility.
It isn’t about Republican, Democrat, or Libertarian ideas it’s about their red button talking points. So you can discuss say taxes or abortion as long as you don't bring politics into it or get repetitive.
What most often confuses people is you can get heavily downvoted or upvoted for expressing the same idea depending on who shows up to a given discussion about say Nuclear power, Bitcoin, etc.