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?
You gave them an irrevocable license to basically use your content in any way they see fit. Them not showing posts you deleted is just them being nice, not being obligated to do so. They could simply ignore your request or restore posts later.
You should have thought about that when you gave them that license to your content.