I liked this story, but thought it ended in a wave of hands and smoke. I think that the moral of the story was that Shannon's passion in the early days wasn't really about the adventure of forging new ground, but rather was a passion for Jet Fuel, and once he realized that, getting that one packet transmitted seemed less important. I was a bit annoyed at their glibness towards Synack's fate, but young people in love can do that sometimes.
Speaking of packets, and referencing to Unblinking's post, that one packet was important because if he could get that one packet along, he could potentially get more packets, and therefore could open up communications between fey and "real" worlds, something that previously could never be done.
Re: the tech. Sending individual packets via pigeon and even light signals is dumb. Packets are structured in such a way that computers like them, and can understand them, and can process them quickly. If you reduce this to pigeon, or scroll, or heliography, it is just plain nonsensical. Use the right tool for the job. Transmit messages in whole via pigeon, then translate that into 1s and 0s, and THEN feed it into a computer.