Comment by ryukoposting

I wrote an INI parser that has numerical, boolean, timestamp, MAC address, and IP address types ;) "advantages" of not having a spec!

Seriously: for application-specific config files, the lack of a formal spec can be kind of a nice thing. You can design your parser to the exact needs of your program, with data types that makes sense for your use case. Throw together a formal grammar for use in regression testing, and you're all set.

Obviously a formal spec is essential for data interchange, but that's why JSON exists. To me, YAML is in a gray area that doesn't need to exist. The same thing goes for TOML, but to a far lesser extent.