After the blackout I deleted all my posts and comments on reddit using the PowerDeleteSuite, and since then I've come back weekly to find comments existing on my account. I've been deleting them by hand now that the API is unusable. Does reddit pull these out of a backup? Do I just now see all of my comments? What's the reason these comments keep showing up?
It's quite clear that King Steven considers all posts the property of the Crown. Even if your deleted post is not recovered right away, if a backup is available it will be eventually.
If you live in the EU, you may have more traction with a GDPR complaint. It seems Europeans have some institutional memory on how to handle Royalty.
I do live in the EU. Does a GDPR complaint help? As far as I know this only applies to personal data, such as emails, names, addresses etc. not comments and posts.
It applies to comments and posts to the extent that they are attributed to you, about you and/or their content is specific enough to render you identifiable. In practical terms, this means that a data controller can in most cases keep the content of your post by anonymising it, which is why when you delete your account it shows "[deleted]" in place of your user name above your old posts. If the content of the deleted posts, even in aggregate, allows me to find out who you are, then you would have grounds to insist that the content be deleted (or sufficiently anonymised).
From my experience, your posts on private subs are hidden so PowerDeleteSuite can’t delete them. When they open back up, those comments and submissions suddenly appear on your profile.