Why do you guys think that when you edit your post/comment reddit would change this specific entry in the database? Anyone designing such a system would just store a new version and keep the old versions to have a paper trail. Same with deleting, you would only mark it as deleted, never delete anything.
And then it's very easy to roll back.
It's possible, but considering the storage cost of not just storing and caching every message on Reddit, but also every revision of it would likely be prohibitively costly, and probably not a priority, there's just no money on it. It's definitely a possibility, yeah, but at least with them doesn't seem likely. Besides, we cannot prove it one way or the other, so worrying about it seems like a waste of time.
But we can see that they're bringing back the comments which have been edited, isn't that the proof? 99% of the content is not edited so the size of the additional eddied is negligible. And I can imagine that they might need to do it because of some legal reasons so that people can't remotely destroy evidence or something similar.