Is it legal to ride on them on the sidewalk? Where I live it is not. It is, in fact, dangerous for walking humans to coexist with scooters on the sidewalk. I personally had many close calls and a few bumps. The close calls would have been serious, possibly fatal, had I not jumped out of the way.
I wonder just how spiky your clothes could be before you'd get cited for incitement to danger. Is it illegal to walk around looking like a discount dime-store Sauron?