We don't. The YAML parser does:

```ruby
if File.exists? File.join(base, "#{name}.metadata")
  # Yay, found metadata file.
  metadata = File.read(File.join(base, "#{name}.metadata"))
  self.data = YAML.safe_load(metadata)
end
```

The file is run unmodified by the YAML parser in exactly the same way the extracted front matter would be. And yes, it does break if the external metadata has `---`, I'm unsure as to the specifics of why.