Seems like the link should be https://backreference.org/2010/02/10/idiomatic-awk/ instead of https://backreference.org/index.html
I'm not sure what has happened then.
<link rel="canonical" href="index.html">
I had to stop submitting ISC SANS posts because they similarly have a canonical link in their head which HN, for reasons I'm not sure about, use to 'correct' the URL, errantly.I can turn that off for specific domains - if you email the relevant info to hn@ycombinator.com I'll take a look.