I've heard it from two teachers and saw a task with a solution based on this assumption:

> 
> If the net torque is zero when measured from one frame of reference, it is equal to zero
>  in all other frames of reference
> 
> 
> 

This actually seems clear, especially if you put it to simple words like:

> 
> If a body doesn't rotate from one point of view, it won't start rotating if you look at it 
>  from another point of view
> 
> 
> 

Still, I wanted to test it and made such an image:
![torques](https://i.stack.imgur.com/P8m9v.png)

I calculated the net torque measured from point A (I'll skip the designations such as $m\_1, r\_1, m\_2$ etc. and get to the value):

$$1m\cdot1N + 5m\cdot1N - 4m\cdot1.5N = 0$$

Now, let's calculate the net torque from B:

$$-2m\cdot1N + 2m\cdot1N - 1m\cdot1.5N = -1.5Nm$$

From this it seems, that the body doesn't rotate around an axis in A, but does around
the axis in B.