Why would anyone be willing to play with fire like this (pun intended) to save a few cents? It boggles my mind. If the few cents you might save by refilling something not meant to be refilled are that important to your financial situation, I would recommend using an alcohol or wood burning stove instead of a pressurized gas one.
But if you insist on refilling your cannisters, be sure and yell "Hey y'all, watch this!" before you begin. That is the universally recognized warning phrase that you you are about to make your bid for a Darwin Award. Others can clear the area accordingly.
Make sure you have a few beers first. I believe that is customary in such cases.

Actually, in practice, I find it no more dangerous than hooking up a stove. Certainly this is less dangerous than using white gas which many people do without giving it a second thought.
HJ