YAML has newlines that indicate the end of a field... unless otherwise specified, which then gets into issues with line endings. Indents can also cause issues,

YAML has newlines that indicate the end of a field... unless otherwise specified, which then gets into issues with line endings. Indents can also cause issues, considering a space inserted somewhere by accident can mess up your whole document. JSON and XML rely on specific tags for elements, which are much more reliable, and thus easier and faster to parse. You can easily add comments to JSON spec, by just writing every parser going forward with the added comment parsing. It would read old JSON non commented files just fine.