Including the PGN tag [Variant "chess960"] solves the import problems, and as far as I've tested, it fixes the castling bug, too.
If a field for [Variant] is added to the Game Details panel in the import wizard, 960 publishers could be wholly in business.
I tested each possible king-rook-rook configuration for the castling bug when publishing 960 games. The bug manifests itself when you insert a game — Chrome and Safari intermittently import as "Standard" rules even after selecting "Chess960" rules.
Firefox never fails, however. So the workaround for this bug is: If you're sharing 960 games with the chess.com publisher, use Firefox, not Safari or Chrome (though Chrome is chess.com's recommended browser).