Adding a coupon before user logging adds shipment fee to the total amount: bug?

[SteP[IT]]

In my setup (vm 3.0.6 + j 2.5.28) I have noticed that when a NON LOGGED user tries to add a coupon to the cart, he gets the discount but the shipping fee is wrongly added to the total amount of the cart!
To test this, simply set a shipping rule with its cost, set a coupon, add a product to the cart and save the coupon BEFORE logging/registering to the site: you'll get the discount, but the cart total amount will be also increased by the shipping fee cost.
I attach here two pics, the first after adding the coupon but before logging, and the second after the coupon addition (previous step) and then logging: you can see the total amount is exactly increased by the shipping fee I set up for that product.
I presume it's a bug: could you please confirm it and eventually provide a fix?
Regards

[SteP[IT]]

No one comfirming that?
Regards