Overclocking your monitor is pretty similar to overclocking a CPU or GPU fundamentally. There are logic transistors in the scaler chip that need to keep up with the signal being fed to it. There are also transistors that will drive the pixels to the value they need to hold. The scaler and panel have an inherent limit to how fast they can go to keep up. You will start seeing artifacts or the monitor won't be able to hold a picture if you try to push it too far, but this is not because your monitor is being damaged, it's because it can't keep up. The only way to get transistors to keep up with a faster clock is to increase the voltage (this is what you do when you overclock a CPU or GPU core). Only excess voltage will harm your monitor, any artifacting due to OC should be cured with a power cycle to reset all the logic at worst. There is no way to increase the voltage to your monitor's circuitry, so there is no way to overpower and therefore damage your monitor.