It seems that the acquisition normalization does not compensate for cases when the IJK to RAS matrix is linear but non-orthogonal. As a result, a slice view may be set up with non-orthogonal axes, resulting in distorted appearance:
@pieper could you have a look at the acquisition normalization code if this behavior is expected? It would be better if the IJKToRAS matrix in the volume would be always orthogonal because at many places this may be assumed. The acquisition transform could contain the skewing operation.