That seems a bit contrived, but it would be similar to if someone else posted your home address in a comment. Presumably emailing HN to request its removal would be the correct thing to do and I wonder if HN would remove the PII.

Edit: it's covered by HN Privacy policy which is available here: https://www.ycombinator.com/legal/

TLDR: email [email protected] for privacy concerns which should cover removing comments.

In my opinion, that seems compliant with GDPR.