The discount is valid for all UA flights worldwide. Yes, valid on H fares. But good luck getting UAL.com to offer an H fare!

I finally was able to get it to work. I didn't chose the upgrade option, but did find flights I wanted where the lowest inventory available wasa "V" fare, so the SWU upgrade would world.

Truth is, I wanted a different return flight. Ended calling the 1K desk. I explained the problem. They understood that if I refunded and bought a new ticket, I would lose the 15% discount and pay a higher fare. Agent was able to revalidate my ticket onto the flight I wanted at no charge. She heard my frustration with ual.com and called her support desk to made an acception,