How much can people be trusted? How well does an open modlog and the ability to move instances work as a means to keep abusive mods in check? That's basically what the question comes down to.

I have no doubt that well-meaning and good natured mods could put post and comment editing of others to good use to improve the end user experience for most users. But these kinds of tools are also easily abused, and in worse ways than simple banning and deletion. For this reason, disallowing editing is definitely safer. But is that tradeoff actually better? I don't know.