"Somebody" is right. And wrong. Excessive wall voltages can be a problem with some amps. Some devices DO have regulators that correct operating voltages. Most tube amps DO NOT. For example, a vintage amp designed with a 110V primary that has a 4X step-up at the secondary will now have an 68 volts of HV. If the amp was already pushing the limits on the stock circuit, like a pair of el84's at 340Vp in class A, you now have 408Vp idling at over 100% dissapation. You'll probably blow something up. There are also some power transformers that fudge high on things like tube filament taps. If the PT has a 115V primary and is designed for 6.8V on the filament tap you'll get about 7.5V on the tube filaments. That's over the max tolerance for this circuit and may cause premature tube failure. But in general, most devices designed for 120V will be fine with the extra 7V on the mains side.
If your using vintage gear this would be a good subject to learn a little about. If your using modern gear don't worry about it.
P.S. Not sure why, but wall voltages have been going up and up for a long time. Some PT manufacturers now offer 125V primaries even though 120V at the receptical is the (much ignored) standard. And, FWIW, 127VAC at the receptical isn't uncommon. It probably fluctuates during the day.