Replacing the Ks line with
Ks 0.0 0.0 0.0
made no difference whatsoever in the rendered image.
I deleted two of the offending objects from SH3D, both from the Catalog pane and from the 2D layout pane. They disappeared from the 3D preview pane. Then I edited their .mtl files and reloaded them using the menu item Furniture/Import furniture.... After placing them appropriately in the 2D layout, I generated a photo using Sunflow at the next-to-highest quality level.
The two objects are still displaying reflections of each another in the rendered image.