Fun fact: they remove the little nub in the middle of the peanut (called the "heart") before making peanut butter. Apparently the heart is more bitter than the two halves.
Observed Fact: If you make butter in blender from Lidl Salted Peanuts it is (very) good only for a day or two, thereafter it tastes little bitter. But you can compensate by adding raisins to the blend.