Well, an (overly flexible) reading of that policy is that they won't simply delete a story from their website without a trace, but will allow themselves to repl

Well, an (overly flexible) reading of that policy is that they won't simply delete a story from their website without a trace, but will allow themselves to replace the story with an retraction and explanation if the story is so flawed that it can't be fixed. (You'd have to make the dubious interpretation that "content" refers to the story as a whole unit, rather than the divisible text.) In fact, this is really the only interpretation consistent with the practices of NPR and many other new organization (e.g., NYTimes) of making repeated edits to stories without leaving the old versions online; instead they simply note that edits have been made, and summarize them. It would be weird if they could freely delete wrong statements from an article but not delete the entire text of an article if the entire text is unjustified. Of course, I agree with most HN readers that the most transparent, ethical, and self-consistent policy is to keep a complete edit history of the story available.