The tw-title is using h4. For sites that need compliant with WCAG 2.0, this creates a nested headings problem if the tabbed widget is placed above another widget that uses h2 or h3 heading.
See:
http://www.w3.org/TR/UNDERSTANDING-WCAG20/navigation-mechanisms-headings.html
Would be nice if the plugin provides HTML Markup settings for "Before/after title: ", and option to get right of <span style="display:none;">...</span> before <h4 id="tw-title-4-0" class="tw-title">...</h4>
Thanks!