Am I correct in saying that this page (and related) doesn't say how to to make queries list (only) non-existing pages i.e. red links, nor whether it's impossible? Or is it implied somewhere I'm not seeing? Perhaps it's implied somewhere that a page must exist for a semantic property to be declared about it?
Example: I want to make a list like http://wikipapers.referata.com/wiki/List_of_authors , but for pages which don't exist.
No, it is not possible to query for non-existing information. Setting a boolean property on existing pages for links which point to non-existing pages using the #ifexist parser function may be a way out. Thus you can query for this information.