Alternately, if work appears on Steemit, whether or not it is past payout, it should never be offered “for sale” in digital form anywhere, for any reason. Permafree on Amazon would be acceptable. Exceptions would be if the work is part of an anthology or offered in physical print.

I don't think it's quite so black and white. There's something to be said for providing convenience in packaging and offering a paid version to enable people to essentially tip for the material. As long as users know that all the versions exist, why not give them the option of providing a convenience?

I'd love to be able to use some of my amazon dollars to buy an ebook or anthology of some of the content I've seen on steemit, provided that the actual authors got the payout.