Blogger team has diversified the authorization to make comments by providing OpenId support for blogspot platform.
What is OpenId: OpenID is a way of having decentralized online identity and which can be used anywhere OpenID is supported.
Now with the OpenId support, users can make use of their OpenId url to get authorised to comment on blogspot platform blogs.
How to get an OpenId?: There are many free providers of OpenId. Its very easy and simple to get your OpenId. I would suggest you to get an OpenId from myopenid.com, which is absolutely free.
So, power your comments with OpenId. Its like a single key for all your locks!!!.
Related: OpenId decentralized and secure login for multiple sites