"To sum up: MMT is wrong about money. Even supposing that it’s right, its impact is fiscally marginal. The government does have a budget constraint."
He is reasonably well informed about MMT and has presented an argument that has attracted Scott Fullwiler, Warren Mosler and JKH's comments, among others. Good discussion.
UPDATE: This is a good place to mention a previous post by Jack Sparrow at Seeking Alpha, The Trouble With Modern Monetary Theory. It is not as well argued as the post by Rognlie, who is familiar with the MMT literature while Sparrow is not. Scott Fullwiler, Warren Mosler, and Pavlina Tcherneva comment briefly. There are over 300 comments.