I think it was an awesome idea, and I went up 3 levels in Reach with the cR it gives you. I went from 3,088 cR to 100k+. It was fun finding them, and writing down the codes, then entering the correct code on Waypoint.
I wish more Halos would have codes you enter on Waypoint 
I agree. There were a lot of mysteries buried in CEA, and the terminal codes are just one of them. I’m glad 4 followed in it’s footsteps in that regard (Section 3, etc.)
It was very awesome! Plus you got some backstory on guilty spark and it made you think, i wonder how i can find more codes
Im kinda hopping this goes on for Halo games. Adds much more to it. I loved the Keys video.