>by being extremely strict about indentation, both in terms of the parser & also community convention. YAML hasn't

This is why I created StrictYAML. A lot of the pain of changing YAML goes away if you strictly type it with a schema but you keep the readability.

Counterintuitively that also includes most indentation errors - it's much easier to zero in on the problem if the error was "expecting status code or content on line 334, got response", for instance.