this could also be explained by sketchy scripts failing to completely delete posts/comments, which i even noticed myself when checking that they had done their jobs properly. as i mentioned in another comment, i had to run the shredder scripts several times for complete overwrite/deletion. or it could be database errors failing to register edits/deletions due to extremely heavy loads at the time. it could be a lot of things.
the point is that we don’t have any direct evidence of what it actually was, just a lot of circumstantial evidence and a lot of speculation. nothing definitive.