According to /u/Spez, Reddit CEO, the reports of messages edited without any user consent or knowledge are correct as he admits to have done it so himself:
Hey Everyone,
Yep. I messed with the "fuck u/spez" comments, replacing "spez" with r/the_donald mods for about an hour. It's been a long week here trying to unwind the r/pizzagate stuff. As much as we try to maintain a good relationship with you all, it does get old getting called a pedophile constantly. As the CEO, I shouldn't play such games, and it's all fixed now. Our community team is pretty pissed at me, so I most assuredly won't do this again.
Fuck u/spez.
The edits were made in a thread linked from the Washington Post which described the recent ban of the /r/pizzagate subreddit which tried to uncover child-molesters and recently moved to voat.co.
(Score: 2) by NCommander on Sunday November 27 2016, @03:27AM
To my knowledge on Reddit, subbredit moderators can only delete posts, and not edit individual ones. I never bothered to setup the reddit.com source code so I don't really know the full scope of admin powers over there. In addition, I can understand in some cirmstances unrestricted editing is warrented as long as its posted that it does happen (usually in forum rules), and there's notification that it has happened.
For something like a harm reduction board, hosting something like that on USENET would be extremely tricky due to the almost non-existant availability to delete posts (yes, I know cancelation messages exist, most servers ignore them for better or worse).
Still always moving