Preserve tab spaces
The tab characters are actually converted to <span class="tab"> <!-- tab --></span> element in initial conversion, but it is removed in the conversion pipeline, this happens at the 15EDITORIABASIC.xhtml where the span elements are removed. well, the track-changes for tab character are preserved properly with <ins> and <del> which was added earlier.
Only the elements <pre> and <code> in HTML can render the tab spaces. Here my question is how these tab spaces are handled in Editoria or Wax.