I don't think he takes creator feedback as automatically inadmissible, so much that he treats it as unreliable
I don't see anything in RationalBrony's comments which adopts anything like your suggestion of taking out-of-universe material as an unreliable source and cross-checking it against other materials, previous statements etc. - as makes sense, since this is perfectly ordinary pre-Death-of-the-Author literary criticism & scholarship! (This is, in fact, the exact method I aspire to in my own Evangelion research & criticism.) Let me quote from the Wikipedia article on "Death of the Author":
Barthes's essay argues against traditional literary criticism's practice of incorporating the intentions and biographical context of an author in an interpretation of a text, and instead argues that writing and creator are unrelated.
I don't know how much plainer a denial of your suggestion one could get! Hyperbole nothing.
So RationalBrony is either so incompetent that he thinks the exact opposite of the actual view he is claiming to espouse, or you're simply being way too charitable and forcing a sensible view onto someone who is not.
I suspect a case of semantic drift and cultural myopia to what happens outside his cultural environment (he did link to the TV Tropes article on DotA rather than the Wikipedian one). After all, we do call ourselves rationalists, yet, unless we link someone to lesswrong or engage in a lengthy explanation, people would call us out on "thinking the (near) exact opposite of the view we are claiming to espouse".
On TV Tropes, when someone says "death of the author", they mean "the author's opinion and his precendents are an optional sour...
This is my first attempt at starting a casual conversation on LW where people don't have to worry about winning or losing points, and can just relax and have social fun together.
So, Big Bang Theory. That series got me wondering. It seems to be about "geeks", and not the basement-dwelling variety either; they're highly successful and accomplished professionals, each in their own field. One of them has been an astronaut, even. And yet, everything they ever accomplish amounts to absolutely nothing in terms of social recognition or even in terms of personal happiness. And the thing is, it doesn't even get better for their "normal" counterparts, who are just as miserable and petty.
Consider, then; how would being rationalists would affect the characters on this show? The writing of the show relies a lot on laughing at people rather than with them; would rationalist characters subvert that? And how would that rationalist outlook express itself given their personalities? (After all, notice how amazingly different from each other Yudkowsky, Hanson, and Alicorn are, just to name a few; they emphasize rather different things, and take different approaches to both truth-testing and problem-solving).
Note: this discussion does not need to be about rationalism. It can be a casual, normal discussion about the series. Relax and enjoy yourselves.
But the reason I brought up that series is that its characters are excellent examples of high intelligence hampered by immense irrationality. The apex of this is represented by Dr. Sheldon Cooper, who is, essentially, a complete fundamentalist over every single thing in his life; he applies this attitude to everything, right down to people's favorite flavor of pudding: Raj is "axiomatically wrong" to prefer tapioca, because the best pudding is chocolate. Period. This attitude makes him a far, far worse scientist than he thinks, as he refuses to even consider any criticism of his methods or results.