We are on a roll! I did it last night as well. Nothing spectacular.

Tanaqui, you are exactly right, the same thing happens to me in both lucid and non-lucid dreams. I feel it is a part of sleep paralysis that keeps you from shouting.

It seems also for me at least that REM, and especially lucid REM can be a shallow and fragile thing, especially late in the morning. So don't worry, you are normal!