Great! I've put the new Chopin-CD in the German wikipedia-article about you (http://de.wikipedia.org/wiki/Edna_Stern#CD-Ver.C3.B6ffentlichungen).
I do completely agree with your argument. But I wanted also to say something behind that: sometimes the composer himself may not be completely aware about his ideas (this, at least, is how I understood Leonard Bernstein when he made his very psychoanalysis-inspired interpretation of Robert Schumann' scherzo in the 2nd sinfony and wanted the orchester to play it in such a way). From the notes, it is note by note Schumann. But nevertheless, this interpretation goes beyond that. It corresponds to what psychoanalysis claims in many cases of Art, that there is often something more, coming from the unconsciousness. And sometimes we find really intriguing interpretations, that do both correspond to the idea of the composer and correspond to what we know about the biography, the context and the psychological circumstances. In many cases, I think the latter would be overdoing the interpretation, but in some cases and works it makes sense, maybe even in Bach's work (from http://en.wikipedia.org/wiki/The_Art_of_Fugue) - but there is also some discussion about that as you can read in the same article:
"Contrapunctus XIV breaks off abruptly in the middle of the third section at bar 239. The autograph carries a note in the handwriting of Bach's son Carl Philipp Emanuel Bach saying "Über dieser Fuge, wo der Nahme B A C H im Contrasubject angebracht worden, ist der Verfasser gestorben." ("At the point where the composer introduces the name BACH [which in modern notation is B♭-A-C-B♮] in the countersubject to this fugue, the composer died."
So was the introduction of B-A-C-H on in a very complex fugue Bach's presentiment of death?
And even more provocative: could Beethoven's 9th sinfony also be interpreted in the sense of a superimposed overhelming joy, but there is naked despair beyond. I konwo that this is very uncommon and maybe it is simply wrong, but for me the "song of joy" often sounds this way.
To summarize: I think that you have posed a very intriguing question, and it is really hard to find any concluding answer. In contrary, it poses a bunch of interesting philosophical questions about understanding, interpretion and communcation.