FWIW, when the postderef feature was taken out of experimental status, it was elected to leave the "experimental::postderef" warnings category in place but to make it a no-op.

As is good practice and as I would expect. But the next thing I would expect to eventually happen would be to clean out really old cruft by making references to 'experimental::postderef' deprecated and cause a warning and then to later make it fatal (by removing all mention of it from the source code). Not that I'll make any predictions about approximate time frames for such. :)