Why is there so much less kibitzing on IGS as compared to KGS?

I don't really know, but I think it's because IGS was founded in the early days of the internet, when chatter was not so common. I think over time it became sort of an unwritten rule not to comment much except for during broadcasts. Furthermore some actually like that there's less chatter on IGS (I used to be one of them) and gravitate to it for that reason.

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"Those who calculate greatly will win; those who calculate only a little will lose, but what of those who don't make any calculations at all!? This is why everything must be calculated, in order to foresee victory and defeat."-The Art of War