The old now obsolete code is xmp. If a site/browser supports pre HTML4 it might do something if you use it, but implementation was always buggy. If you use it on DW now (in Firefox anyway) it displays escaped code, rather than displaying the code. But you could use it as a code generator with the preview function.

So if I type in <user name=facetofcathy> with the xmp tags around it, I get..

&lt;user name=facetofcathy&gt;

And if I take what that shows on preview and paste it in my comment...

<user name=facetofcathy>

I get displayed code.