On the newest version of three.js, the normals as seen on the node material example are flipped.
This is what it looked like before the latest release:

@sunag could this be related to recent changes for clearcoat normals?
I think that It is because the pertubNormal2Arb in NodeMaterial was update, now pertub2.. result is diferentes with double-sided material. I am working for NodeMaterial get the core functions in runtime.
For testing (latest dev version)
https://raw.githack.com/mrdoob/three.js/dev/examples/webgl_materials_nodes.html
I still am not sure about change this, apparently with use node material and without NodeMaterial the result (MeshStandardNodeMaterial x MeshStandardMaterial) is the same? I have to test this with other sides to assure if this is really a bug or a not.
Maybe this is a bug of the function pertubNormal2Arb from the core?
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I think that It is because the pertubNormal2Arb in NodeMaterial was update, now pertub2.. result is diferentes with double-sided material. I am working for NodeMaterial get the core functions in runtime.