I am flying China Southern LAX-CAN-KTM, i'm a US citizen and contacted the Nepalese embassy here which told me to just get a visa on arrival in Nepal.

My concern is denied boarding by China Southern due to absence of the Nepalese visa and ignorance of the visa on arrival rules.

What can I do to protect myself from denied boarding if the China Southern staff is ignorant and insists on a visa?

I have read other travelers have had this issue in the past where airline officials are ignorant of the actual visa rules and/or if their computers (which may be inaccurate) do not specifically tell them it's ok they require to see a visa.