...a deletion
discussion among
non-professionals is not the proper way to determine the law.
Neither is the opinion of a legal expert: That's the job of the courts.
Courts are the proper way to determine the law after the fact. But
this is a question of determining the law before the fact. Except in
very limited situations, courts don't do that.
Commons editors are only trying to weed out copyright
infringements without
falling for copyfraud.
That is absolutely not true. The deletion policy is much more nuanced
than "only trying to weed out copyright infringements".
If non-professional Commons editors shouldn't be
deciding which images are
PD, then they shouldn't be deciding which images are copyrighted either, and
not one image should be deleted whatever evidence of its copyrighted status
comes up. I don't think that's acceptable to anyone here.
You've made quite a few incorrect assumptions there.
Of course Commons editors should be deciding which images are PD. But
when there is a dispute, it makes no sense for people who don't even
know what a derivative work and an underlying work are, to be
discussing the applicable law.
Anyway, the deletion process obviously doesn't work. File:"Appreciate
America. Come On Gang. All Out for Uncle Sam" (Mickey Mouse)" - NARA -
513869.tif is clearly not public domain. And File:"Appreciate
America. Come On Gang. All Out for Uncle Sam" (Mickey Mouse)" - NARA -
513869 - cropped and tidied.png is probably a copyvio. Yet both
remain, despite deletion discussions, marked as public domain. (The
deletion discussion over the latter is especially humorous.)