Yandex is the company whose sites actively fight ad-blocking more than anyone else of whom I know. Afaik Yandex is just not in the uBO lists anymore, because it was no use changing the filters again and again. So I guess Yandex might allow installing filters which can't catch it anyway, but I wonder if it won't cripple the extension somehow for good measure.
their browser doesn't affect functionality of ublock, but it's not good browser anyway, trying to show down your throat many intrusive features by default
