This filter is a port of Donald Graft's MSmooth.
It smooths the image while not blurring edges. This can be very useful on animation, particulary cartoon animation(nbsp)(ndash) the filter is effective at removing mosquito noise as well as effectively smoothing flat areas in anime.
As an alternative, you may always want to consider the FluxSmooth filter for animation as well (which is a spatio-temporal smoother, while MSmooth is a spatial smoother).