The revolvers that would fire all rounds with one trigger pull were generally the black powder models, not the later models that used metallic cartridges. Even with the black powder revolvers, many people were loading them with paper cartridges that held the powder and ball in place rather than using loose powder from a powder measure. Then the shooter would poke a small hole in the back of each paper cartridge before placing percussion caps over the nipples. The paper that contained the powder and ball was meant to burn up almost completely when the powder ignited, leaving the chamber empty after firing. Generally with these designs, the percussion cap spark and the powder ignition would not cause the adjacent chambers to fire. I know plenty of people who are using modern replicas of the old black powder revolvers that are basically identical in design and function to the originals, and none of them to my knowledge worry about multiple simultaneous discharges.
The black powder "revolvers" that were most prone to firing off every round simultaneously were the multi-barreled pepperbox designs. The unexpected discharge and recoil of six or more rounds firing at the same time could indeed damage the weapon or the shooter's hand.
