I’ve written on this several other places, but: the Quora editor natively supports Plane 0 Unicode characters, and has a mathematical formatting command, unicode{xHEX}, to allow Plane 1 characters. The majority of characters considered emoji are Plane 1. What you are seeing are the minority that are Plane 0.
With the mathematical formatting command, you can enter any emoji you want in Quora. And you will be reported shortly after, though that may involve a hasty edit to the current formatting policy. As Alexander Lee discovered with his use of red text.