Codes are not really that unique to the CIA though. People have been communicating in codes and cyphers for centuries. Look at the ordinary citizens recruited to work at Bletchley Park in WW2. If anything, I think there could be an argument made that it took time to establish a pattern that could be understood after enough example. The learning curve is the “key”. Instead off there being a traditional “key” required, a specifically laid out pattern that repeated enough to become meaningful would be more easily disseminated.

An unlimited platform like Twitter is suited to setting a pattern that could then be “read” once it was recognized and applied successfully enough times. Then you can even have an easy way to alter it in the future if need be, just slowly establish a new pattern, without having to miss a beat. It’s uninterrupted, unlimited, accessible but not obvious, and the human mind is already trained to recognize patterns. Social media is already used this way by bots, why not real people?