Wrong G authorship (owner is first comment-writer)

Hi,

This is the problem:

The authorship of some posts is the first comment-writer instead of the author. When the author replies he becomes the owner of authorship again.

WordPress version: 3.5.1
WordPress SEO version:1.4.7

What I did:

1.) I set up the Author-Meta-Tag and Google Publisher Site settings in the plugin and followed Yoast instruction from the help pages and blogposts (https://yoast.com/wordpress-rel-author-rel-me/)

I expected the plugin to do this:
The Plugin should put the Authors Name in each post, and enable google to find the authors name automatically, so that the g+picture and authorship is on every search result.

Instead it did this:

Only some post have a g+picture in googles search results.
Sometimes another person has the ownership of my posts. (First comment writer)

You can see that here https://tinyurl.com/m3zwe7w (Google search results)
Blogpage: https://www.hebammenblog.de/

Home someone can tell my, what I did wrong!?

Best

PS: The Googles snippet testing tool cannot find the authors name automatically on the website, when doing the emailvarification. Everything else seems fine.

Boris

https://www.ads-software.com/extend/plugins/wordpress-seo/