## # x-fields:

Since new PMD keys: can be added anyhow, there's little need to use `# x-prefixed-names:`.

  * Instead I would reserve this for "uncommenting" standard fields.

  * Or very temporary additions or documentation-only values.

Examples:

 * `x-poshcode-id:`
 * `x-archived:`
 * `x-generated-by: bison`