You can't judge seed quality by the appearance of the seed, except in really obvious cases. By far the best way is to test germination, as David did. I have seen lots of nice fat seeds that did not germinate. There is also a more professional tool, the tetrazolium test.
http://www.nature.com/nature/journal/v159/n4048/abs/159748a0.html I don't know if any amateurs are using this method.
I can understand why there would be doubt about seed of Anemone japonica. It has a long reputation for being pure fluff. I've heard that if you have only one clone, you will not get good seed. For example, if you have one clone of a Lilium species, and it sets seed, it almost certainly is not pure seed of that species, but a hybrid with some different nearby lily.
Even if you examined the seed under a microscope and it looked OK, it might still be dead because of high temperatures or the passage of time.
Anyway, thanks David for taking the time to test your seeds. We should all follow your example. Imagine a novice grower failing repeatedly to grow seed from the exchange. I don't think it's good for the club.