I heard it was bad luck to open an umbrella inside a building/room. So I wanted to try and see. (Hence, curiousity killed the cat phrase).
I opened it...and WHAM! Without meaning to, I poked my eye and gave myself a black eye.
I don't know if it is a superstitious thing, but I sure ain't ever gonna do that again! ;
Yeah, I think the umbrella thing is more about 'common sense' haha.
i.e. you keep it closed because there might be less room inside, causing you to poke yourself, or someone else, or knock something over.