The voltage change would be only 1/121, since the ratio of the resistors is such. The reference won't change, but effectively it does by shifting the input signal by that ammount on the non inverting pin. There you will see a small jump when the voltage crosses the threshold. That's there as you said to generate hysteresis, so the noise while crossing the line doesn't make the output to jump back and forth before settling, or if the voltage crossing is too slow, the output could act as a linear amplifier making strange things, for this circuits you usually want some ammount of hysteresis.
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