Not only can the safety pilot not log time as IMC if under IMC, he/she cannot log ANY time. What if the pilot keeps the foggles on while under IMC? This doesn't matter. Safety pilot's are referenced under 91.109, which is *simulated* instrument flight rules. In actual, you don't need a safety pilot, and therefore the safety pilot can't log time.

It makes sense, right? The safety pilot's purpose is to make sure that you don't hit other airplanes. What are they doing if you're in IMC? Nothing, so why should they log time?