'Cloud' is not solid, and you can see varying distances in it. Since normal formation separation is only a few feet you can normally see the next aircraft. Normally, and particularly when there is a lot of 'movement' in the formation, is is important to see as much of the rest of the formation as possible so you do not just react to a sudden movement by your 'neighbour'
On the occasion to which I referred it was bit thicker! The leader got a bit more abuse from us than usual in the debrief
