I don't think this is a great resource for understanding the argument.

> Level 3 thinks Cogent should have to pay them, because the balance of traffic isn’t equal, but Level 3 doesn’t think it should have to pay Comcast, even though that traffic is also lopsided. Confused yet?

Someone seems to be. He's confusing a peering arrangement between two tier 1 providers with a dispute between a tier 1 and an ISP. The tier 1 providers have other ways of routing around each other, but there's only one way to get the bits a comcast-owned person requested to them: through comcast.