Pete Holzmann has written an excellent Firefox-Greasemonkey add-on that provides comment capability from the old site for Firefox users (which I use BTW). Go to https://climateaudit.org/ca-assistant/ and try. It will make commenting easier. Thanks, Pete.
Update: the CA Assistant page has been updated with hints on enabling/disabling GreaseMonkey, enabling the script for other WordPress sites, and more.