I have implemented OpenID commenting here, and I have gone one step further, by allowing commenting only after logged in, while using OpenID. This isn’t to avoid comment spam, which I think it will happen regardless. I am encouraging the use of the technology, which others might consider flawed (the CardInfo lovers, etc).
All OpenID providers are accepted, of course. I have even setup a small OpenID server of my own as well. Lets see how it goes.