The ignore function is an admission that the poster you dislike is right and you can't prove otherwise. The reason the poster is ignored is that the ignored poster forces the would be ignorer to question their beliefs and preconceived ideas. Many people hold these ideals highly and simply won't entertain anything that questions them. Try talking to a devoutly religious person about their beliefs and they'll soon make a swift exit for the simple reason that you make cracks and fissures in their belief model that cause them grief. They can't help but admit they are wrong but simply don't want to accept that fact. The ignore button is just the same. Basically, it means the poster is putting their fingers in their ears, closing their eyes and going "la la la la la...." then thinking they've won the argument. I love that button, it's hilarious. It means that I can disassemble a posters argument without their even having a right to reply. It's great. It's like having Prime Minister's Question Time against a Prime Minister that is deaf, blind and mute.