>>3749
>do commoners have a moral obligation to serve a king that is deliberately working against the best interests of the nation?
Yes, and national interests are hard to define. Unless you jump into extreme hypothetical situations with the king opening up borders and doing all this wild stuff we see in the age of republics. For most cases, it is best to be loyal and obedient.
>best interests of the nation
However you define this, I wouldn't understand. This could really be dependent on circumstances and those always could go for best or worst. A king could become a vassal and have a foreign presence, but the king is still someone to be loyal to and you can still oppose the foreign presence. There are real monarchists who have done this and became martyrs for their royalty.