Wouldn't that be too much acid?
I'm guessing you are talking about this recipe: https://food52.com/recipes...
The author talks about the buttermilk and baking soda in one of the comments "From a scientific perspective, the answer to many of these concerns is this: if you make the cut in the butter properly, leaving large (walnut half sized) pieces of butter in the dough, there is a significant amount of natural leavening from the steam created when the butter melts inside the biscuits (the article attached to this recipe goes into greater detail). Because of this, there is a "medium" amount of added chemical leavener, which is then activated by the acid in the buttermilk to create the total leavening.
That being said, if people aren't mixing properly or are having trouble, more baking powder could be an answer. Adding more baking powder will make taller biscuits, but it won't create flaky layers like the handling of the butter does - which is what I'm looking for when I make biscuits. I've tested the recipe again with some of AntoniaJames suggestions, and doubling the baking powder to 2 tablespoons produces a taller, lighter (fluffier) biscuit. It's not as flaky, but it's light and pretty darn good! Hope this helps some of those biscuit trouble-shooters out there!"
And you also might want to check out her related article on them: https://food52.com/blog...
Thanks for your thoughts and experience! So do I need to use shortening to get flaky?
I asked the Erin, the recipe author, and she says: "No, not necessarily. Shortening has a high melting point, which means it's easier to work with than butter, which melts under the heat of your hand. If you follow the steps and chill the dough when directed, butter will work just as well, and taste way better."