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 wow, it took me a few minutes to figure out what was up with that thread--and I knew edited posts have the date and time underlined, but I wasn't aware about the mouse-hovering thing that shows who edited a post and when.
I'm still confused, though. What did frodocooper actually do to those members' posts? We're not talking about a mod writing stuff that a member didn't write in his post, correct? That would be supremely fucked up, but that kind of sounds like what OP is complaining about.