Question about feedback in a current reference
The change in voltage with current is greater on the resistor side than on the transistor side when the current is in the normal operating range for this circuit. 

The derivative of voltage with respect to current is R on the resistor side and the dynamic resistance of the diode on the other side. At, say, 1uA the dynamic resistance will be around 26K ohms. With around 0.5-0.6V across it (to match the voltage drop of the diode-connected transistor at 1uA), the resistor will have to be about 500-600K so it will be much higher than the dynamic resistance of the diode. 

Note there are two different things going on here- the bias point is set by the resistor relative to the (more-or-less fixed) diode drop. The stability depends on negative feedback so the derivative of the voltage with respect to current.