I like toml even more than json, but the real issue to me is that we, or most of us, have this subtle drive to generalize, and the more things we can make comfigurable the better. But as it is said, when something is fully configurable that is like saying it isn't done and assembly is required. Also, we end up designing declarative domain specific languages. But I don't want to program in json, yaml, or toml. They aren't made for that, and it hurts me. For rust the clap crate helps put the brakes on if you agree on a simple rule, anything that is a config file parameter is a command line argument and environment variable. It is one struct that gets populated by the combination of those things. If you wouldn't make it one of them, don't make it any of them.
