Mirrors and workarounds should be in the post to begin with. No link (not just on HN, on the internet) should lead to paywalled content without clear indication. Providing a mirror or at least spelling out the best workarounds (Yes every.single.time) should be mandatory.

Edit: I understand it could be controversial for HN to officially push links that pierce paywalls. But a tag users can avoid wasting time would be appropriate, just like a link to a discussion of common workarounds.