Ummm... I believe those of you who are seeing two "converging" pistols are not focusing on the front sight. I think you are focusing on the target instead. When I focus on my thumb at arm's length I see one thumb. Same with the front sight. I do see two light switches, door knobs (with thumb) or targets (with pistol) though. At arm's length you should be able to focus on your thumb with both eyes without seeing two thumbs. Anything past the front sight should split into double vision as your line of sight from both eyes will cross at the sight and be offset past that.
I find it extremely hard to shoot with both eyes open so I don't do it. I don't always totally shut my left (non-dominant) eye but rather I just squint it enough to eliminate or blur the image of the "second" target in my "double vision". It's just a lot easier for me to do that than to deal with the double images of the target.
Being right eye dominant though, if I align the image of the front sight with the image of the target to my right hand side I can hit the target. When it comes down to being liable for every round I shoot though, I don't want to be dealing with two images of the target to choose from.
Si vis pacem, para bellum...
"An unarmed man can only flee from evil, and evil is not overcome by fleeing from it." -Jeff Cooper