I noticed something that seems to be a bug in seller coupons creation.
I registered myself as seller to do some tests.
I tried as seller to create a coupon for my products. I noticed that I was able to specify the seller to whom apply the coupon.
In addiction I was able to create coupons also for products of other seller.
In my opinion this is not correct. A single seller should be able to create coupons only for his own products. Only staff member should be able to select sellers to which create coupons.