Not sure why anyone really expect companies to allow then to use their own tools to screw them. All that data is backed up several times even if the delete actually deletes the comment and edit actually replaces the comment. But it can even be better for performance reasons to just remove the reference or point the comment content at a new comment while the old remains somewhere. Writing a script to undo the mass deletions/edits might have been trivial if they also keep a record of the previous data in the comment's db entry.

Even the legally required ones only really matter if an audit catches them and the consequences are steep. And the auditor isn't willing to look away because of some sort of kickbacks or job offers after their time auditing.