don't see what value we'd gain from storing
that extra metadata. Every
scenario I can think of where you care about past states of the database is
already handled by the compare selected revisions feature.
If that is so simple, can the {{#property:xxx}} call in a wikipedia
simply resolve to the revision that was valid at the point in time
equivalent to a given revision? It seem like you say you already have
the code to do that when creating the wikidata item description.
I disgree that this is an issue for mediawiki core, since it is a
question of how the Wikidata-specific property function works.
Gregor
PS: I admit that Denny has found an example to where an image seems to
be changing in content on commons, but I still believe this is a rare
case. Any wiki-statistician that can supply exact number for these
cases?