Hello Thomas,
The Authors section was removed in version 2.1.1 (build 20101018) because it was not relevant to custom-layouts.
Please see the change log note, copied for your convenience, below:
Removed the Authors section from the Publish toolbar because it was not a per-layout setting.
If you want to have different layouts based on different authors you will have to make separate member groups for those authors who share specific layouts.
This is explained in the Saving your Publish Page Layout section of our user guide.
I have earmarked that reference to Authors section of the toolbar in the documentation to be removed to avoid future confusion 😊
Edit: Bug report can be found here
Best regards,
Barry