I came across today one of my own comments on Reddit with a search on duckduckgo. It was still intact. The problem is I used shreddit to randomise and delete the entire contents of my account. My account comments and posts all show empty on my account pages on reddit so there should be nothing.
I did a site:reddit.com search using my username and found ~50 comments that Reddit has undeleted but also hide from my own account. I could still edit and delete them. Its curious that they don't appear on my accounts content on Reddit and yet a search engine can find them and they are still served by Reddit. Ex Reddit users who deleted their account contents should be aware this is happening and report it as a GDPR breach to their respective agencies if they are in the EU if they too find this has occurred.
I thought some of my old posts were restored but it turned out that those subreddits were still dark when I ran the delete script and had since reopened. Don't know if this is the same situation as you but maybe check if that is the case?
Do the comments show up in your account profile under your comments?
Many of these were deleted long before the protests actually and some not in subs which went private. There is no obvious reason why these particular comments are detached from my accounts comments and yet still owned by me and not accessible from the reddit account page.
Sometimes comments are just not properly linked to your profile for whatever reason, I’ve had it happen a number of times throughout the years. You can view them and edit them, but they don’t show up on your profile - exactly like you’re describing here.
I’m not saying Reddit isn’t doing something fucky here, but rather that it’s absolutely not a guarantee of anything malicious.