Agree with this one. Fare rules might be different for different destinations. Even if stopover is allowed, I think you need to arrange it by using TA in Taiwan since the online booking system for USA destinations do not seem to allow stopover (at least for "I" fares). Unless, there's the stopover function appearing in the booking, like the ones they have on specials during the promotion on Feb and Mar.

Right now, they are having Business Class specials for Mainland and European countries (like my ticket), 1 stopover allowed and you can specify the number of days you want to stopover using the online booking system.