I see your point, but I think you draw conclusions too far from what I wrote. I don't argue that the only quality of an interpretation is to what extent it is along the original intents and lines. Of course there are room for creativeness and vision. Changing from clavichord to pianoforte seems like a good improvement, partly because it makes the sound of this night music softer to the ear, which was one of the whole ideas with the composition. What I meant is that playing what is essentially doubling as a lullaby in a forced or unharmonic manner is just not interesting.
I also see that there is a wide range of ways of defining what is interesting or good in music, or fine arts as a whole. In one of the ends of this range, view with simliarities to yours can be found, that the audience's taste is the only thing that matters (perhaps you could call it "quality by description"). In the other end, there is the view that the audience's reception counts for nothing (perhaps "quality by norm"). I guess your more oriented to the first mentioned end than I am.