Rejected as violates ForgiveAndForget.
One UseModWiki feature under consideration (for after 0.9) is to allow people to "keep" a version of a page. Kept pages could be browsed as a regular page or in a textarea editbox (for cutting and pasting into current pages). The number or total size of the kept pages might need to be restricted (due to very limited disk space).
Later... This seems more likely now, especially as a reply to the Wiki:WikiErase question. All kept versions would be made available to all users (similar to the previous-author-copy). I imagine that a few volunteers would keep "good" copies of all the pages they read. (I could do this for Meatball.) An attacker will only be able to erase changes made after the last kept copy. (I'm also thinking that all users might automatically "keep" the last few pages that they edit, at least for a few days.)
Disk space doesn't seem like a serious problem now. Kept versions will only be stored once, with a list of users that kept the particular version. Once the user list becomes empty for a particular version, that version will be deleted. By the time I run out of disk space I will probably move to a dedicated host with gigabytes to spare.
For the long term, I now figure that even 100 times overhead is acceptable (100 Mb of overhead for each 1 Mb of "content"). The C2 wiki had about 20 Mb of "content" as of May 2000 (see Wiki:WikiMines). I could spare 2 Gb for that kind of quality content. (On the C2 wiki, the average page has been modified less than 20 times, so 100X overhead is a pessimistic estimate.) -- CliffordAdams
I question how often people will use this. I suspect people will use KeptVersions as the exception, not the rule. I'll bet people will mostly want to keep a page after discussion has settled down (what's the point otherwise?), but it's difficult to tell when the discussion is quiet. And by the time it's settled, people have forgotten about it. (How many direct questions have I not responded to on this wiki? Too, too many.) --SunirShah
That being said, there is potentially benefit to this, especially on a technical wiki that occasionally requires some sort of versioning (like this one); something better than the ol' manual versioning. Also, it can be useful for "holding the gains" between stable plateaus to the discussion. -- SunirShah
I expect a few of the RecentChangesJunkies will read all the pages, and "keep" any pages that seem OK. Each user could keep one copy of each page--if a newer version is kept, the older version is released (and removed if nobody else is keeping it). I'd also like to help cooperating groups share the load. For instance, one might select others that one trusts, and review new pages not seen by the rest of the group. Other users could also keep pages that they find interesting, and be relatively sure that the kept version will be available later. --CliffordAdams
To deal with ForgiveAndForget, one could disallow keeping a version beyond some time limit (if you liked stuff in your Kept Version that much, you'd then have to get it back into the current page before the limit was up).
If the time limit were short and were the same as the KeptPages limit, a KeptVersions feature wouldn't get much use. If the time limits were identical but long, KeptVersions would be a convenience feature, a way to bookmark a non-current revision. If the KeptPages limit was shorter than the KeptVersions limit, it would serve to alleviate the "look at these changes now before they are permanent" pressure on the community.
I think only the last, two-tiered scheme would be very useful. But it is too complicated to be worthwhile.
The two-tiered scheme would mean that you could make the KeptPages timing much smaller, perhaps to one week. That could make ForgiveAndForget more effective, where the participants wanted to forgive and forget. The payoff is that a KeptVersions expiry of three months (say) would reduce ForgiveAndForget where the participants don't want to forgive and forget. But I don't think you can force forgiveness or forgetfulness on people with a TechnologySolution, so I don't think that's an issue.