I bet they don't actually remove posts/comments just flag/hide them
Most web apps will keep a copy of messages you delete, but they usually do not save an history of every modification.
> When it became known that post edits were not saved but post deletions were saved, code was added to edit your post prior to deletion. In fact you can actually turn off deletion all together and just have lorem ipsum (or a message about Shreddit) but this will increase how long it takes the script to run as it will be going over all of your messages every run.