different usernames for different blogs on one account

When we register a username account here the email address we provide becomes our unique identifier. When we are logged into WordPress.com and register a blog it's registered to that username account we are logged in under and to the email address which is our unique identifier. We can register as many blogs as we wish and provided we are using the same username account then all the blogs will be registered under it and the associated email account. We can change our "display name" but that display name will appear on all blogs registered under the same username account.
http://en.support.wordpress.com/email-address/
http://en.support.wordpress.com/change-your-username/#change-display-name-nickname

In order to completely separate the blogs that you do not want to be associated with each other you register another username account using a different email address when you are logged out of WordPress.com. http://en.support.wordpress.com/register-a-blog/ Then you add the new username account as an official user of the blog, and designate them (ie. you) as an Admin. Next you transfer one of the blogs to the new username account using this process. http://en.support.wordpress.com/moving-a-blog/#transferring-your-blog-to-another-user-or-account

I have started two different blogs - one under a name on twitter (so I am identifiable) and the other I want as an anonymous poetry blog. I had my username as the twittername but then saw that when I posted on the second blog - visualizewhatyoucantsee, this would come up as eg 'john smith posted on visualizewhatyoucantsee's blog' so i changed it to visualizewhatyoucantsee's blog, however as my second blog is also linked into the same account it now works the other way so will say visualizewhatyoucantsee posted on John smith's blog - hence giving away the fact that it me writing both and is therefore not anonymous. I hope that makes sense?? So how can i have two different blogs but have different names showing as posting the content - so visualizewhatyoucantsee posts on visualizewhatyoucantsee's blog and John Smith posts on John Smiths blog - as they are both on my one account?

if anyone knows let me know? Thanks a lot! :D