It seems it is easier for a LH shooter to use since I do not get the dreaded bruised knuckle that RH shooters seem to suffer from.
I'm a right handed shooter and do not dread, or suffer from bruised knuckles due to double triggers. Its not a right hand /left hand thing, its not even a double trigger thing, its a people who don't know/understand the proper way to do it, thing. IN a way its in the same class as people who get their fingers pinched loading Win/Marlin (side loading gate) lever guns. They get pinched or bruised because they aren't doing it the proper way.
Unless your intent is to fire both barrel at the same time, or as close to the same time as possible, you simply don't put more than one finger in the trigger guard.
(for normal sporting use) Your (single) trigger finger goes into the guard to fire the front trigger. No other finger has any business in there. You fire your shot, and during recoil assess the need for a second shot, and if so, one simply slides your hand back on the stock, allowing your (single) trigger finger to pull the second trigger.
IF you do put two fingers in the guard, the rear finger can be bumped (and bruised) by the back of the front trigger, if you are shooting something with enough recoil to do that.
The classic African "stopper" double rifles will SLAM your second finger, due to the heavy recoil, and many of those guns have hinged front triggers to help protect the shooter from that.
Many folks apparently have never been taught the proper way to use a double trigger gun, and since it has two triggers, they think you use two fingers, and if/when the gun "bites" them due to recoil, they blame the gun.
Same kind of thing for people who get their fingers pinched by the loading gate of a lever gun. It's because they aren't doing it the proper way. Using your fingers to push in the rounds does work, but you can get pinched. Using another ROUND to push in the ammo also works and NEVER pinches your finger.
There are guns where holding the gun one way lets it bite you, and doing it slightly differently does not. My Grandfather taught me the "right" way to use his Ithaca SxS 12 ga. At least as far as the triggers were concerned. What he didn't teach me was about putting my thumb over the wrist of the stock. The GUN taught me that, by giving me a split lip the first time I shot at a bird with my thumb in the "wrong"
place, for that gun....
HIS gun had the stock made to his order, and it has more drop than common, to fit his slender lanky frame. Worked flawlessly for him, but for me (and other people with a slightly different body size/shape) the result is the gun comes UP in recoil a lot more than other guns (and it does it rather hard!)
What it taught me was that pushing off the safety and wrapping my thumb over the wrist of the stock (which is what I normally did with every other shoulder arm) was the way to get my lip split by my thumb knuckle as the gun came UP hard in recoil.
Only made that mistake ONCE!
Grandpa never taught me to avoid that, simply because the gun never did that, FOR HIM!..
THe only other gun I've ever used where I make a deliberate effort to ensure my thumb is alongside the grip and not over it, is the Win Model 97 shotgun.
If your thumb is in the wrong place when you pump the action, there are sharp edges on the bolt that can slice your thumb quite painfully. (but only if your thumb is in the "wrong" place
)