It is answered in the FAQ [1] and re-iterated frequently by dang.
Paywalled pages are OK if a bypass is available. If there is one, usually someone will post it in the comments.
If nobody has yet, you could try viewing the article in http://archive.is/ or https://outline.com/, and if it works, share the link here.
If no paywall bypass is available, the item should not be on HN, so you should flag it.