It's hard to say, but I wouldn't call the moon microgravity, it's at 1/6th of Earth gravity. The moon particles are more jagged and also often statically charged, which may help or be a hindrance.
Plus there's the whole spacesuit thing, those gloves make it hard to do anything, let alone build a small structure with fine details like a sand castle.
On the other hand, the combination of microgravity, no wind, and more jagged sand particles might lead to better cohesion
It's hard to say, but I wouldn't call the moon microgravity, it's at 1/6th of Earth gravity. The moon particles are more jagged and also often statically charged, which may help or be a hindrance. Plus there's the whole spacesuit thing, those gloves make it hard to do anything, let alone build a small structure with fine details like a sand castle.