In D14893#400604, @Brecht Van Lommel (brecht) wrote:

I think the point of this change is to get rid of the normalize in object_normal_transform? However object_dir_transform is not exactly the same. For non-uniform scaled objects it's important to use the inverse transpose matrix. So the better solution may be to add a object_normal_transform_unnormalized function to use here.

I need vector n to be treated as an elevation above a triangle and to be transformed as if there was a point. object_dir_transform does the trick. My experiments also show that object_normal_transform_unnormalized would introduce new artifacts:

It's a shadow from the right object

You're right, seems to be fine as is.