Some additional notes:

The counter-stretching is not the source of the problem. While it is used 
here to make the problem more obvious, the normals will be evaluated 
incorrectly when a UV map is stretched, no matter how the normal is scaled.

I would say that the problem manifests itself in almost all uses of UV maps 
with normals. At least on curved surfaces, mapping a planar texture onto it 
will *always* result in some amount of stretching.

I don't know if the behavior is a bug or a limitation. In any case, as long 
as it is there, artists should be very cautious about using normals in 
combination with UV mapping.

Rune
-- 
http://runevision.com

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