Each persons taste buds are unique, and have their own unique sensitivities.
Baking powder is one of the things which becomes unpleasant for most people once there's enough of it to makes its presence known through the taste buds. One component of double acting baking powder is a "dry acid," while another is a type of heat activated acid called a pyro-phosphate. In sufficient quantities, erreither and/or both can trigger the "bitter" buds. That's usually not a good thing in a blueberry muffin.
While 1 tbs of baking powder per 2 cups of flour might not be too much for some people, it is for many other. It seems likely your friend is among the second group, while you're not.
As I wrote eariler, the common maximum ratio of baking powder to flour is 1-1/4 tsp to 1 cup for quick-rise baked goods; and 1 tsp to 1 cup is probably more common. I suggest reducing the amount of baking powder from 1 tbs to 2 tsp on your next run -- if for no other reason than to eliminate a superabundance of baking powder as the cause of dissatisfaction. Chances are good 2 tsp will give you the same amount of rise that 1 tbs did. However, if you get good taste but not enough loft, you can try 2-1/2 tsps of baking powder on the following batch.
It's worth memorizing both the maximum and optimum ratios. If I can remember 1 to 1-1/4 tsp per cup, so can you.