[imtringued]

I once found a .cfg file. It had an incomprehensibly foreign configuration format that is specific to the file. A standardized config format like YAML or JSON has lots gotchas but you can learn them once and then know forever. With custom_format5345 you have the problems of poorly designed configuration formats (lots of gotchas, sometimes more than YAML) and the downsides of having to relearn the undocumented configuration format.