On 2013–08–17 Dmitriy Tokarev wrote:

> I noticed that after the command \kerncharacters, I can not use
> the normal sequence "---" for em-dash. Is there any work around of
> this effect?

This is expected, since \kerncharacters breaks ligatures and the ---
→ — transformation is implemented using the ligature mechanism. You
can either use — or \emdash. Since -, – and — are hardly
distinguishable in the source, I'd settle for \emdash.

\starttext
  foo --- bar\par
  foo — bar\par
  foo \emdash\ bar

  \kerncharacters[.5]
  foo --- bar\par
  foo — bar\par
  foo \emdash\ bar
\stoptext

Marco