I don't think they are actually restoring posts/comments. This whole thing is based on confusion about the blackout and many subreddits going private. Most people would think you can see all of your own posts and comments if you are logged in and go to your profile page, but if a subreddit goes private you cannot even see your own submissions in that sub.

So after the blackout ended and most subreddits went public again, people who nuked their account history are now discovering that there's still posts remaining. They think these posts were restored, but they weren't even deleted in the first place.

This is obviously a huge oversight on how Reddit handles your data and your profile page, but don't attribute to malice which is adequately explained by stupidity.