I have always held in the clutch on all my vehicles. That way I am ready when the light changes. It hurts nothing...it is what they were designed for. If you held it for hours at a time, you could overheat the throwout bearing, but a few minutes, intermittently, does absolutely no harm.
I do not believe that anything you can do at a light really prepares you to avoid an accident. Either way, you're liable to get walloped. If you watch the rearview mirror, to try to avoid a rear-end incident, you won't be watching traffic, and could easily pull into somebody's path when you react to what you see. If you don't react, you can get rear-ended. Either way, you lose.
-Scotty