Hi,
I suppose that Jerome is talking about the "Give points when using some" setting of the user points plugin that you can find when you edit it via the menu System>Plugins.
However, from what I understand, that setting will only not give points when the discount on the product is made by points.
But, from what I understand again, you're talking about discounts configured via the menu Orders>Discounts which is something different. So in that case, that won't help you.
The only solution I can see without changing the code it to create an unpublished category, add it to all the products with a discount and select that category in the "Product categories" setting of the plugin. In fact, you might already be restricting your discounts to specific categories and in that case, you can use these categories in that setting.