I was just going to reference that same post, Peggi!
If you don't feel the Kona at Joann or anywhere else is "up to snuff" and it says Kona on the end of the bolt, you should send some to Kaufman Fabrics as they suggest in the post.
Kona is often less expensive online at fabric.com or some of the other larger retailers than at Joann. Right now it's $5.48/yd.
One thing you won't find at Joann is the more expensive Kona black, which I think is triple dyed. It's priced slightly higher but well worth it for a nice solid black.