Burning fossil fuels, even with advanced methods to limit the harmful outputs, is still burning fossil fuels. You can make coal safer, you cannot make it safe. That's just part of the deal, if you want the energy that comes from it you need to accept what comes with said energy. Coal is safer than it used to be, it's not purely safe and it never will be.
Clean coal is not 100% safe. However, one must also specify within which context is the safety in question. Would this be safe to operate machinery with? Probably. However, clean coal is still essentially founded around a finite resource. So is coal safe for the future of our economic development? Probably not.