Of late, from several directions, I've observed debates over whether certain interpretations of source material constitute fanon. Don't worry if you've never heard the term. It's a bit nebulously defined, and what it means is something of the topic in and of itself.
When people talk about fanon, I think there are actually several distinct concepts in play. In the long and difficult task of interpreting a work, readers often make assumptions to try to fill in the gaps in stated facts. To reference tvtropes once again, it would be an assumption to state, for example, that balance within the force is balance of good and evil. It's a natural assumption, coming at Star Wars and the light and dark sides as constructs of morality, but it's also just that--an assumption, something not specifically stated, even though it seems sound and, indeed, common or ubiquitous. A fair bit of what's called fanon falls under this category: people take literal text and extend it perhaps one or two steps too far. People think the text says more than what it really does say.
But there's another type of fanon, one that differs, perhaps, only by a matter of degrees. This is where people totally make up story elements and those elements become accepted and treated as if they were canon. As you can imagine, this is most prevalent coming from fanfiction. One particularly popular work, with a totally valid means of filling in holes in canon (like, say, Akane's mother's name) can be referenced in other works as a shout out or whatnot, eventually spreading to the point that nobody can remember where the name Tendou Kimiko came from, but suddenly, a bunch of people assume that's Akane's mother's name. As you can see by this example, when one person invents something on their own, with original creativity, it's merely doing what a fan-author needs to do in order to tell a story without having to avoid the unfilled canon pot holes. It's the morphing of this once original, invented element into something treated as fact that makes the idea fanon.
Or does it? Does any suspect interpretation of the source work make that idea fanon? Or is it the statement of that interpretation as fact that makes it fanon? It's the difference between being factually inaccurate and factually unsubstantiated, between "not known to be true or false" and "provably false." Of course, any interpretation likely relies on several different elements, each of which may be one or the other and in total make all assertions fall on a continuum, an plane with axes of certainty or uncertainty and truth or untruth.
Perhaps I don't really know what fanon is, either.
