Mentioned by @tstoeckler in:
ConfigStorageController currently uses public properties of the ConfigEntity object to write the yml file.
If the ConfigEntity is coded according to our standard, this means properties in CMI files will be camelCased.
That constraint wouldn't apply to inner keys in the yaml tree, and since most of them would come from array keys, they would be underscore-separated strings.
This constraint also wouldn't apply to non-ConfigEntities CMI files which, coming mostly from variable_get(), are underscore-separated too.
--> nasty mix :-(