It's not really clear to me HN comments are even covered under GDPR's right to deletion. The GDPR doesn't guarantee wholesale deletion of every bit of information you've posted on the internet (by that standard you can also demand some open source project scrubs your name and email from the git history, and all comments on the issue tracker/PR reviews).

Accounts can be renamed, and specific comments can be deleted, which seems to cover GDPR in my reading of it.