There may be a case that you need to show multiple contributors to a blog post, or a verification/certification of a specific post. In which case you will have the use of the Alternative Author setting in Author Signature very useful.

This option allows you to specify the name of another one of your defined Authors and have that Author load within the Signature instead of the post author. 

The author name can be provided via metafield - which when combined with the display options allows you to only show the addition signature if a valid author is available.

This provides a simple and stylish option to add multiple authors to a post