> Who ultimately determines the meaning of a public space: its designers, authorities, or the people who use it?

Restrooms are unique in that they are available to the public but, due to their inherently private nature, are a place where it is difficult to enforce social norms. Because of this, within the confines of the restroom itself, the authorities are all but irrelevant.

I was scrolling through the addictive and easy to stumble into YouTube reels feature and came upon a livestream of a gentleman having some sort of 'public restroom party' in a stall. By this, I mean he had collected every roll of toilet paper available, shredded them into confetti, and was throwing the confetti up into the air while blasting music at full volume out of his bluetooth speaker. He had a few thousand viewers and people appeared to be donating money for supercomments. I didn't stay to watch the end of the livestream, but I don't imagine he cleaned up.

By the time the private-but-livestreamed confetti party is over, the damage is done. You can try to anticipate every single unwanted activity in a restroom and try to prevent it beforehand (e.g. tinted lights to prevent IV drug use), but someone, somewhere will find a way to creatively make the owners decide a few frustrated customers who are told "no public restroom" is a small price to pay for the alternative.