Regarding your two-stamp case, did the immigration officer gave you two stamps only because you had the Taiwan tourist VISA?
Let`s say, if I plan to both enter and leave Taiwan using my Taiwanese passport, do you think I will still be granted another stamp on my American passport upon leaving the country? In this case, I have no tourist VISA on my American passport.
And now my question is leading to this one.(sorry...I`m making this so complicated...) When entering the U.S, does the immigration officer look for the stamp you obtained when entering Taiwan or when leaving Taiwan? or both? If both, don`t you have to ask for two stamps upon arrival, as well as departure?