We don't edit them or change them. We would remove them and the account involved.
And no moderator of even admin can do it. Only myself. It's usually a dodgy message that first gets reported to us. Then I have to login the database and run a search to erase the others they sent.
Like I said. Every single website can do it.
Messages are not sent end to end encrypted when on any platform or app unless stated. Like WhatsApp is. And it tells you when it is secure.