Textile supports the following markup:

lazy writing – and theft

to render:

writing—and theft

(taken from http://www.textism.com/tools/textile/index.html)

Confluence just leaves it as two dashes. And if I type this:

writing – and theft –

Confluence renders that as:

writing <del class="deleted">- and theft -</del>

I think that in both cases the "--" should render as an emdash.