A couple things....
Great plugin, by the way, works perfectly.
A few thoughts on what someone may be able to do. I'm no programmer, I just come up with the idea's lol.
I think it's great that if I have one email address being used by multiple accounts, whether they are WP or FB or Google, it basically treats all those different logins as one user!
But then there are those pesky API's like Twitter and LinkedIn among others...
Regarding the @example.com emails that some networks create (Twitter, LinkedIn). Stinks, but not much we can do. At least it populates the users actual twitter.com site in the website field, so at least that way you can communicate with them if needed.
After I learned how that worked, I then started troubleshooting the missing avatar in the comments section. Worked everywhere else. I didn't see it in the few posts I read about it, but turns out that If I have an existing site, and there are comments already on it, then I install the plugin, It will not populate those previously made comments. Only new ones.
It tends to change the avatar to whatever avatar / network I'm currently logged in with.
Now, what if there was a way to force those pesky API's to not populate the "E-mail (required)" field, but instead, populate a twitter specific, or hidden field instead.
Can that be done? I think that would fix a lot of headaches.