Yes, in the "Market Theme" options area, there is a setting to remove the comment marks.  The other place to remove comments is in the regular WordPress settings area.

You certainly can create different product sub-categories. 

You of course need to have a main product category named "Products" or "All Products" or something like that — but you can have many child product sub-categorys placed under the main parent product category.

To do this, just create a category — but just make sure to specify the parent category as your main "Products" category.