[GuB-42]

I think that making the signal look natural does not need an intent to hide.

It is simply a result of Shannon's entropy. To be detectable, signals have to be broadcasted and low entropy, the opposite of what we need for efficient communication. A signal that makes best use of its bandwidth would be indistinguishable from noise for someone who doesn't know the protocol, it is also likely to be precisely targeted at the recipient and unwanted emissions kept to a minimum in order to limit interference.

It is already happening on earth as we are replacing loud analog TV emissions with more subtle and better targeted cell phone signals.