On 2013–08–20 Martin Moncrieffe wrote:

> Finder reports that my version of Hoefler is 8.0d2e1.

This means we already have three different Hoefler versions in this
thread.

> […] shows the the em dash is present in the font.

When I use a version with em dash, your example works here. Someone
using a Mac is probably in a better position to help out.

You can also try to use simplefonts, it works for me:

\usemodule [simplefonts]
\setmainfont [Hoefler-Text]

\starttext
  A test of Hoefler at 10 pt. The  emdash--- does not work...
\stoptext


Marco