I set a voucher code to add a free product in the cart (no free shipping, reduced amount etc...)
Quantity available : 1000
Quantity available per user : 1
I placed an order using this voucher (payment chèque), then I switched the order status to "payment accepted" and I placed a second order with the same user account using the same voucher : I could place the order without any error. So the same customer can place an order with a voucher restricted to 1 per user...
Prestashop 18.104.22.168, default bootstrap theme/clean install.