As opposed to DocumentMode and ThreadMode pages (see also WikiModes):
FileMode pages are usually created through the misguided efforts of inexperienced wiki refactorers.
FileMode pages present a shapeless clump of vaguely related information adhering to no distinction and conveying no consensus.
FileMode pages often conceal gems that once were pages in their own right, but it takes a patient and determined reader to discover these now.
FileMode is strongly discouraged on WikiWikiWeb - refactorers take heed.
When you see a page in FileMode it is usually better to fix it and not waste time making yet another WikiBadge for it. FixYourWiki.
AnswerMe please:
The above describes what's wrong with FileMode, and how it comes about---but it doesn't really describe what it is. I've read this page from top to bottom and I still can't figure out just what makes a FileMode page a FileMode page.
Any examples here on Wiki?
Hopefully not, but you might consider WikiWikiSandBox an example (though it really is AppendMode?).