Thanks for reaching out. The product reports you are referring to can and will handle discount codes/coupons/adjustments on your orders. I dropped into your account and noticed that none of your stores are setup correctly to show this information on your product reports. Take a look: http://note.io/1VqpMIJ
This setting is basically telling ShipStation to ignore line item adjustments/coupons/discounts on your product reports. If enabled, newly imported orders with discounts will start creating a product record and will begin to appear in your product reports. Take a look at a sample report from a store with this setting enabled: http://note.io/1ouZye3
You can enable this setting by heading to your ShipStation account clicking on Account Settings > Selling Channels > Store Setup > Edit > Products Tab. This setting does not retroactively apply to your current orders, however, it will start reporting the discount for newly imported orders into ShipStation.
Hope that helps!