Deleting a post is simply marking a piece of text so nobody sees it, but I think the text is still stored in their servers.
Furthermore, a large company like reddit, must backup regularly, meaning there must be several copies of my posts in several SSDs. If the backup once a day… some of my posts are 5 years old.
Companies exist to make money. I suspect they just marked my posts not to be readable by anyone, except staff and they can still monetize them.
Am I wearing a tinfoil hat way too often?
Depending on what they do it’s not that simple. If you include the entire history of an account you could probably de-anonimize most active users. That being said, de-correlating the comments and posts before feeding them to an AI model is probably enough.