Unmatched {- does not allow - to be part of em/en-dash

[hellux]

For the current implementation, if the opener is unmatched, the hyphen does not get parsed together with
later characters, e.g.

• {--- generates <p>{-&ndash;</p> instead of <p>{&mdash;</p>,

• {-- generates <p>{-- instead of <p>{&ndash;</p>.

[jgm]

That's true; it's an artifact of a parsing strategy that tries not to backtrack. It's not too worrisome because this is unlikely to occur naturally.