In reference to Blogger the issue is on the other end. Blogspot software assumes we all have a single username here at wordpress.com and only a single blog by the exact same matching name. It will not accept any other URL - invalid URL! it says. Ha!
So if we have a domain or more than one blog registered under the same WordPress.com username trying to comment becomes impossible, unless the blogger chooses to enable commenters to post with a username and URL on their Blogger blog.
The only workaround is to register a Blogger blog which will allow you to comment but your username will not be linked to your WordPress.com blog when you do. Then you are labeled as a 'no reply blogger'. It's crazy-making!
Open ID has always failed more often than it has worked.
Bottom line: This is a well known issue. If you simply use the Name/URL option when it's provided then your blog will be linked to your username on the comments you leave on blogspot blogs.