I read something about it a long time ago, saying that it should be opposite from your dominate eye. Apparently helps you aim better o_O I use left hand but it took me a while to get used to it.

Many of the good players I know said left is better but couldn't explain themself lol.. I don't think it makes any difference whatsoever except there will be an adjustment period and switching is pointless unless you know why your doing it.

It has to deal with your dominant eye.

This is correct for all competitive gaming, mainly becuase having more open space on the domininant side of your screen gives you a slightly better reaction time. If you play worse when using this tut, either let it go or practice, since obviously your playing will be affected; you have to get use to it. Overall well written and a great example of why left/right side options are tweaked in competitive gaming.

Im left handed, but right eye dominant so I fire a gun with the right side and so i just keep it default right

I dunno, i like left-hand better.