You're referring to the YAML point? The way I read it, it sounds like the poster only learned about the issue when they ran into it during development. That being said, a couple of specific complaints is probably not the best argument against a broader platform.
I remember XML support in .NET being excellent. The author could have used C# classes that would serialize/deserialize to/from the XML, then used built-in tools to generate an XML schema for the config files. The schema could then be consumed by vendors or other connected projects using .NET and have perfect, code-first, statically typed interop. You'd never be writing XML itself or the schemas or the serialization/deserialization code. You can't get any of that with YAML, it doesn't support that sort of safety. You'd have to manually implement all the safety checks and serialization/deserialization for a worse end result. Of course that would be a bad outcome.
