This is an impressive article. I'm not very familiar with hardware debugging, so I would have given up if I saw the exact same input yielding different outputs on the device in wireshark.
According to the BBC, the entire sub is bolted shut from the outside, so even if the vessel surfaces, the occupants cannot escape without outside assistance and could suffocate within the capsule.
Why is the submarine bolted shut from the outside?
Alot of vendors (Lenovo[0], ASUS, Dell, ) are using Windows Platform Binary Table, WPBT (https://news.ycombinator.com/item?id=18095848) to get the OS to execute binary. Dell seem to use it to load the Absolute's Lojack anti theft rootkit[1]. Also on Absolute's website there's a list[2] of manufacturers that are using Absolute Persistance[3].
I remembered watching a youtube video[0] about it. The "vertical bar" 124 / 0x7C is in the original 7-bit ASCII standard. But the 166 / 0xA6 "Pipe, Broken vertical bar" is in the not so standard high ASCII/ Extended ASCII [1].
I really agree on the user signed bootloader part. I think we should also have this for Android devices, since most Android devices only have two years of system/security update.