Hi Theo,
Yes, at the moment the discounts and coupons are not summed up - a bit later we will implement a feature that will let customers apply the coupon without summing up the discounts.
At the moment, you can go to your settings and preferences and unmark Customer Loyalty Discounts checkbox. This will let your customers use your coupon - and you to test out whichever campaign works best for you.
Regards,
Eddie, CGTrader