>Giving people with multiple citizenship more rights than people with single citizenship would naturally cause problems, and yet you don't want citizens with different rights as that would indeed create different classes of citizenship.

You just mentioned multiple citizenship means multiple taxation... That's "more obligations", not "more rights". You are not making any sense.

>A person can also end up with one citizenship in a country that allows multiple citizenship, and one which does not, and the citizenship of the person then depend on which country is being asked.

...What? You don't make any sense. I know Japanese people who live in Switzerland. Switzerland accepts dual citizenship; Japan doesn't. The stricter country wins out, and they had to choose whether to be Swiss or Japanese, full stop.