Run examples/widgets/widgets/styles with Norwegian wood and XP style you will notice the radio buttons missing text from currently selected item.
Both styles run common style code where we end up with a pen only having brush color and that leads our text drawing code to bail out. Some reminiscent of glyph outlines perhaps.

 
void QWindowsDirect2DPaintEngine::drawTextItem(const QPointF &p, const QTextItem &textItem)
        if (qpen_style(d->pen.qpen) == Qt::NoPen)
           return;

There is another bug where text is not getting rendered in that example, but that seems to be about clipping.