Don't shoot the messenger.....I had to look this up as it has changed If its any consolation, I don't agree with it.

Customers requesting a change from a published nonrefundable fare to a higher published fare may upgrade if all qualifications are met and the ASC will be waived. The ASC will be waived only when upgrading to a Y or higher fare.

On International fares, it depends on what the PEN paragraph says.