The conversation is about metallic cartridges. You're not likely to have a chain fire with paper cartridges out of a cap and ball but using no lube at all will bind your cylinder up so fast it'll make your head spin.
Metallic Cartridges i.e. 45 Colt: Not much chance of it happening because of the cartridge itself seals and contains the powder. A chainfire via the front of the cylinder would only happen if the bullet got dislodged by recoil and by dislodged I mean way knocked loose. A chainfire from the back would mean that a primer didn't get seated all the way and didn't jam the gun when you rotated the cylinder. Both of these situations are highly preventable. I've never heard of a chainfire in a metallic cartridge revolver, but I lead a sheltered life, it probably has happened to someone somewhere.
Paper Cartridges: Likelyhood of a chainfire when loading paper cartridges is the same as when not. I shoot a LOT of 'em. Properly fitting caps and roundballs are your best insurance against a surprise. Don't count on grease, wads, cornmeal etc. to stop a chainfire.
Just so you don't get the wrong idea, I use cornmeal for filler and I use Crisco for lube. Both because they work and they're cheap. Besides, my wife hasn't missed either one yet.