*TODO*

In the source format of Markdown with with annotations...

* the syntax for annotation **should* be relatively human comprehensible
  (in the same spirit as Markdown -- e.g. \*\*strong emphasis\*\*)
* annotation syntax **must not** conflict with core Markdown
  (i.e. must not cause disambiguations)
* annotation syntaxt **should not** conflict with other Markdown extensions

For syntactically correct and structurally supported annotations...

* visual output **must** be identical to source without the annotation
* metadata of output **must** contain the annotation

For syntactically incorrect or structurally unsupported annotations...

* the annotation **must not** disappear from visual output
* visual output **should** include the annotation in source form

## Plan

*TODO*
