Actually, the widely used commenting system Disqus is the one that changed the down arrow policy in the last couple of days. I assume NRO uses Disqus, but I suspect they had little to do with the change, although they might have had input into the decision I suppose.
Are you sure that it was Disqus? Or is it just a Disqus option that NRO recently implemented?
I hate this change on discuss, I LOVE thumbs downing people’s replies. I wish I could do it here!