It turns out it is very easy,
http://bug-attachment.wikimedia.org/attachment.cgi?id=5997 ,
to squeeze current duplication out of the text table, for we the little guy.
I suppose I'll just do that often, as there is little interest in
stopping new duplication coming in.
Who cares when you have all those fancy backend intelligent storage
systems.
But when all you use is MediaWiki, then you're on your own when you want
to reduce the size of your mysqldumps, compressed or not.
However, when undoing the *last* edit, it is indeed
equivalent to a
revert. Perhaps MediaWiki could make use of that.
Just check to see if the sizes are equal, then if the texts are equal,
https://bugzilla.wikimedia.org/show_bug.cgi?id=18333