I think in that article Roger is mostly talking about a lateral differential, which he assesses is unnecessary with a quilt. He's absolutely right, it's practically useless.
However, there is an argument for a linear differential in winter type quilts. i.e. a longer top shell piece than bottom piece, will cause the down to loft outward from the inner shell, which can really help to avoid compression or tight fit with normal quilt sizes. Just my opinion.
Anyway, I don't recommend going over 1/2" per baffle. You can get a really puffy quilt by doing a linear differential and slightly shorter baffle height than normal.