I had the same response - and the photo rejected (still life of a skull) had nothing in common with anything in my portfolio! That being said, I like both of your images!
Could be the moderators selected the wrong reason. It would likely have been rejected due to the post processing. You may find better success submitting the color version of the file. A designer wanting to use your image can easily convert from color to black and white however, the reverse is not true. Submitting black and white photos severely limits your potential customer base.