I'm afraid that won't stop people from trying for it though.
It's the Pink Elephant effect, we can tell people that there aren't negative levels but it won't stop some from testing it out. Which means a lot of negativity coming from them in order to get back down to 0 to try it.
It's counter intuitive, but it will become a pseudo achievement for some people to remain at 0.
but it's still not actually worth anything, and people care about levels.