I have a dilemma.
If I look at the diagram and say the sum of the forces in x and y direction has to be zero, then I will simply conclude that the force of a wall on a revolvable rod is the blue N as drawn.
But what if the force is actually the green N? To me, it makes more sense because if imagine no tension and no mass M, then the force of a wall N would be drawn as below (green N).
So how can I argue that the orange component of N does exist? If it exists...
If I look at the diagram and say the sum of the forces in x and y direction has to be zero, then I will simply conclude that the force of a wall on a revolvable rod is the blue N as drawn.
In addition to the requirement that the sum of the forces be zero for translational equilibrium, it is also required that the sum of the moments about any point on the rod must be zero for rotational equilibrium. See below.
So how can I argue that the orange component of N does exist? If it exists...
You can argue that the orange component does exist in order that the sum of the moments about the end of the rod supporting the weight M (point B on the FBD below) equals zero.
Note on the FBD the tension force and gravitational force on M do not contribute any moment (torque) about the point B. The two forces $F_{g1}$ and $N_H$ both create a counter clockwise moment about the B. For equilibrium, these moments must be balanced by an equal clockwise moment. The orange component of $N$, $N_H$, is needed to provide that clockwise moment.
Hope this helps.
