See regs and how the Volt compares here: Brake Light Actuation
also compares amount of Volt L deceleration to that of manual downshifting in other cars.
Summary: The Volt's L deceleration is below the limit (JUST below) requiring the brake lights to come on, while a Mustang 3-2 downshifting is 2X greater than the Volts, Accelerating a Mustang in 2nd and then taking your foot off the pedal (no downshifting) also decelerates faster of the Volt in L. All this is to say, the Volt in L meets the existing safety regulations for brake lights and is certainly less of a hazard than at least some cars with a manual transmission that are downshifting or simply not accelerating.
The "I Feel" comment almost always comes up when the poster desires the brake lights to come on while in L, regardless of the law or facts. But it's a feeling rather than a fact. and there is a simple solution, don't use L or tap your brake pedal if you "feel" unsafe.
Keep in mind it is a fact that brake lights do not prevent being rear-ended. An inattentive driver will rear-end a parked car, a car with brake lights on, a police car stopped with all it's lights going. Happens all the time. But if it makes you "feel" safer to have brake lights on, then tap your brakes or drive in D.