I'm not sure they're 100% GDPR compliant on their approach to user account & data deletion tbh. But I'm not sure and I'm not a lawyer or anything.

Basically their approach to deletion is (or at least, was) that you can ask them to deactivate your account. After this, it cannot be reactivated, your username is unavailable. However, if you want all your comments/content to be deleted, you have to go through and do it manually (this would take me months, personally...) before deactivating your account. If you deactivated your account already, your data and content is still there and you can't go back and delete it (your comments and posts are now disassociated from your dead username). Admins can't reopen your account and can't (or won't) delete it themselves.

This would theoretically be sort of okay, but what we're seeing is that your manual comment/post deletion must only be a 'soft delete' because admins can clearly restore your deleted or modified comments. I'm unsure if they would be able to do this whether you deactivate your account or not - I can't remember if those who have had this happen deleted their accounts before the posts were changed back. However I'm not sure if there's anything more they would do to actually delete your user data if you email legal@reddit.com with a specific GDPR request under art 17 (right to be forgotten). I can't find that online quickly.

I think this would only apply if you are an EU or UK citizen? If you're Californian you could refer to CCPA regulation. A couple other states have different privacy laws too that may help but they're all different. It may be worth posting on a Privacy or legaladvice community on here to ask what Reddit's approach is and if it holds up.