Autodesk's Jeff Bartels explains how to employ Label Style Defaults at the Drawing and Feature level to better manage the properties of Civil 3D Label Styles.
From the Jeff Bartels YouTube Channel.
and the Civil Immersion blog.
Jeff's short explanation of the LSD (Label Style Defaults) hierarchy in Civil 3D is done really well.
Sadly, he doesn't cover the important LSD level of Feature class Type. For example there are lots of Alignment Label Styles. These have Types like Station Labels that can also be managed with LSD.
A thoughtful use of LSD employed in a Top Down manner allows you to better manage and control Civil 3D Labels.
I trust you get it that LSD also allows you to fix user created Label Style chaos if necessary.