Digital Light & Color

In Precise Gaussian Blur, Chroma Only, is the blur performed on HSV-HS channels? I've tried it as a way of reducing chroma noise, but still have similar issue with dissimilar brightness patches after chroma blurring as described here (try removing chroma noise from the dark suit sleeve image there):

http://www.google.com/url?q=http://www. ... QS1eSOJXmQ