> It’s a markdown editor, but they can’t modify the markdown standard,

They have several modifications of Markdown, everyone has. But not everything makes sense to implement in a flavour of Markdown. YAML is for structured data significant better than a freeform-format, especially when you're in the phase of building the foundation of a new feature-family.

The complain is valid, Markdown is for documents, free form, free flow, structured data are a very different use case, and while YAML is better for the job, it's still a different language with different smell.

But Obsidian is a tool for managing knowledge, always has been; it's not just a plain Markdown-editor. All those features which are going beyond simple flavoured text, have always been part of it's Core-Mission, just not materialized yet.