GDPR only applies to EU citizens though. If the data is truly valuable, I could imagine some work-arounds as well. E.g. maybe each reddit post is automatically a copyright work which you immediate give a perpetual license to reddit inc. You also automatically transfer copyright ownership to reddit inc and they license back your ability to share your comment.
GDPR only protects personal data. If someone requests deletion, you could probably keep the comments as long as you anonymize them (which Reddit does).
Your comments, including here in HN, are probably already covered by a scheme like that where you give the site operator an unrestricted license to use them. You can remove the association to your identity via GDPR, but to take down the content itself you’d need to go through the justice system.
