AFAIK only admins can edit post, not moderators, mods can merge posts and can leave note, nothing more than that.
Moderators can edit the posts.
I remember frodocooper edited many posts on mining board when he was a moderator.
Click
here to see an example of posts being edited by moderators.
Oh, so it's possible. That's a bit insane of moderation based on that thread IMO. I wonder if users get a notification that their posts were edited by a moderator just like a personal message notification when posts were deleted by a mod. Looking at his profile looks like he is not a moderator anymore, idk if its about inactivity since some inactive mods are still mods or its about his way of moderation. I wonder.