Since it was the middle of the night and I wanted to get back to sleep, I sprayed some silicone. This seems to have worked, or coincidence (I haven't had time to lookup the freezing point).
The source of the moisture puzzles me. I am seeing some puddles below the egg's damper, but not necessarily under the valve. I'm using a drip pan under the meat, but the drip pan doesn't cover the entire meat area. I don't notice drippings getting into the fire nor into the center of the fire bowl. I suspect the meat might be dripping down the sides of the egg, and dripping where the vent is. Another possibility is the moisture inside the Egg dripping down the sides.
I think my BGE pit holds a lot of moisture, but I'm just guessing.
Or it could be humidity, freezing temperature, and the fan creating a tiny sheet of ice.