How would you keep an object pointing north no matter what without having to point to a object?
Isn’t a Compass also pointing to an Object? (rhetoric Question – I consider a Magnetic Pole an Object)
Anyway, you could use alignAxisToVect and make your Object point to just a specific Vector. Not an Object.
Which is north x,y or z?
Does it matter?
Direction is relative anyways. Just pick a direction that you like and is convenient to use. I would use any direction on the xy plane.
Linkxgl is right, it depends on the World you create. There is no real “North”. However, if you want a Suggestion, you might use Y as North because if you go to Top View in Blender, +Y is like North on a Map (upwards), so using +Y might make it easy for your own personal Orientation within the Worl you create – it sounds rather convenient in my Opinion.
(Except if you were making a Game taking Place on one round Sphere as Planet, then the Vector would of Course have to be on the Planet’s North Pole.)