Regarding co-GMs, in whatever field the GM will use in future to select co-GMs, there should be an option to toggle on and off permissions for co-GMs. This would cater for both GMs who want to share power with the co-GMs and for GMs who only want the co-GMs as labelled helpers and want to retain the power for themselves.
An edit-backup needs to be time-based, or at least have a minimum time before clearing the history. This would prevent the rogue co-GM/moderator from simply spamming, say, 10 edits to wipe the edit history. The time also needs to be adequate for the fault to be detected and fixed in time. 24 hours may not be enough, for someone could easily spend a day or two away from the Guild. For the sake of revisions, it may also be useful to store a number of prior edits for a longer period of time (or permanently). However, I'm not sure what kind of a drain this may be on the Guild's database resources. I'm just throwing ideas around here.
If you do grant GMs the power over posts in their thread (something which could possibly be abused), then a system which puts the post in a large hider would be safest, for it allows the post to be hidden from view but still available to be read if need be. But a Report button to call a mod to a particular post would be a good idea too. How about give the mods the power to put posts in large hiders? Another tool in their toolbox.
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Oh, in regard to the current discussion on the pages, would a Go To Page # field/button (inside the thread) be too much of a problem? There is no interface option for going to a post in the middle of the thread, and asking users to edit the url is not user friendly. But I agree that we don't really need page numbers from the forum view.