They are messing with you. But the nature of the question tends to invite that behavior. You have been around here long enough for us to expect you to know what voltage ratings mean.
But to give you a direct answer, two things come into play.
First of all, the voltage rating of any electrical device is based on the ability of its insulation system to prevent current from leaking away from the internal wiring to the metal case or otherwise outside the areas where current should remain. If you operate a tool at a voltage that is higher than its rating, you run the risk of breaking down the insulation, and thereby creating a shock hazard.
Secondly, motors tend to run at a generally constant power level. That means the product of voltage and current will remain the same, and if you change one the other will change in inverse proportion. Thus, if you operate a 120 volt tool at 277 volts (an increase of a factor of 2.3), then the current drawn by the motor will be lower by that same factor of 2.3. However, the torque developed by the motor is proportional to the current. Therefore, you will get a torque value that is less than 50% of the rated torque. In other words, if the motor does not flat out electrocute you, it will probably still not be able to do the work you are trying to make it do.
