davem, you are
very inspiring poster
Saucepen, depsite what you've posted about canon, and though I may be repeating myself a bit, I would be glad to have an opportunity to clarify my position some more
I probably failed to communicate this, and maybe it is the try to eat the cake and have it (or may be you are exaggerating a bit too), but was I driving at was more or less what follows:
A) Tolkien's world is Tolkien's entirely
B) Any writing of Tolkien's is canon
C) No other writing is canon
But, having in mind those three maxims, the accounts inside the scope of those may contradict each other, and yet all be valid. All one needs to do is place oneself
inside the story.
So I was in no way implying that other 'explorers' can disprove what 'first pioneer' have said about the world. But if one is to suspend his disbelief (which is an easy task with Tolkien), and place oneself inside the secondary world as 'found out" by Tolkien, than all rules that work in our primary world are perfectly intact inside the secondary one. We may argue that Gandalf of the Hobbit is truer than one of the LoTR, or vice versa, but it would be similar to, say, our choice between intepretations of some event as broadcast by different news stations, and matter of taste and reasoning grounded on it, like in our primary world I tend to prefer BBC broadcast over CNN, but I realise that neither of those gives really true account of what happened, for there may be countless other accounts catching some other angles of it. But, I do not go to the opposite and and do not say by it that any of those accounts is entirely untrue. With Tolkien, the whole evaluation process is inside the secondary world, otherwise processes are similar.
And, as I've said already, the secondary world is defined by what Tolkien have wrought. Inside this, we are free to work out truer versions of anything for ourselves, but are not allowed to add something from outside. So, the bark eaters, which do not originate from what Tolkien himslef wrote, can not be credible but in fanfiction, but, given source material we have, what can be 'revised' and 'combined' out of it can be.
What would be the value of such a 'revised' thing? The same as any broadcast has. Or any history primer has. For it is understood that no primer reflects history as it really happened. And it can be argued that one primer is therefore enough, but primers are written and published dozens by year.
Take the much discussed providence for instance – our research of the case is limited by what is given inside the texts by Tolkien. Some interpret it this way, and some other, but in any argument they are forced to lean on their sources – i.e., by what Tolkien said about the subject. I can not have a valid argument if I say it is drawn directly from the ME as I have had a vision of it in a dream last night (however archetypal my vision may have been, or even if I try to convince you that it was like to experience of Notion Club Papers, and I have been in communion with Elendil himself who have told me so and so), but have to give you an excerpt from the text which is known to be written by Tolkien himself. Those are my limitation, but we all are free to interpret our sources in different way. This is our freedom.
Or, to give another analogy, let us say that genuinely Tolkien texts are stones, and our interpretation is house we build out of those. There are no more stones around than what Tolkien left us, and no one can create another stone. But what house each of us will built out of given number of stones, is entirely up to ourselves.