Not really since it's true. It isn't markup, it's a configuration file format. "<em>This</em> is a markup language" since there is text which is marked up. YA

Not really since it's true. It isn't markup, it's a configuration file format. "<em>This</em> is a markup language" since there is text which is marked up. YAML/JSON is a way to serialise fairly common data structures (arrays/lists, hashes/dictionaries, numbers, strings, bools, etc.) Incidentally, if you can seamlessly replace XML with something like JSON, then you probably aren't using the 'markup' bit of XML.