QUAIL has always had a few awesome reporters available, from one that just listed all the problems, to a fully, WAVE-like WYSIWYG preview.
However, when editing HTML content, it's also useful to just view the actual code and see exactly where the problems are. As of revision 199 of QUAIL, there's a new reporter called codeHighlight which will do just that: put a span of a certain class (for test name and severity level) around every issue found in the code.
There are some issues which arise from the way PHP's DOMDocument rewrites poorly-written HTML code, but that's similar to what any good browser does anyhow.
This reporter will be available in full releases of QUAIL by version 0.4, which is slated for the end of this month.