Using HtX to talk about HTML is a challenge. I've made a first attempt at an environment that will help with this, based on Mark Leone's suggestions. It is called the html-display environment: it first displays HTML markups in place, then provides a button to an ancillary file containing the markups that will display as intended. Here is an example:
<ul> <li> Item 1 <li> Item 2 </ul>
One problem is obvious: the HTML display loses its format. I will fix this, but it will take some tinkering with the HtX engine itself.