DFC,
I think what he's saying is that if you change the course setting 180 degrees when flying a VOR radial, you'll still use the HSI the same way. Fly towards the bar to get back on the chosen radial. The to and from flags will change, but not the way you use the instrument. Do the same thing on an ILS approach and you'll have to fly away from the bar to get back on the localizer, as the HSI in ILS mode does not consider the course setting.
Cheers,
Fred