Showing gameplay would be pointless because 99% of the gameplay is in player's head, analyzing the code, maybe even writing some down on paper. If you just look at the screen, it doesn't make much sense.
It's hard to pick any point in that 75 minute video that would be a good trailer material. There's nothing visually spectacular except some static ASCII art and there's no surprise mechanics that would draw attention. The game itself isn't about ASCII art anyway, so having that in the trailer wouldn't make you learn much.
But then again, it isn't a game for everyone. It's for people who are into hacking, computer internals, binary/hexadecimal numbers or assembly/machine language.
I think a gameplay trailer could be made from content from that video, by stringing together a series of short clips. Show the player moving around, manipulating things. Each clip a few seconds in length. Similar to the trailer for Exapunks, you could display text like "Solve puzzles" "Manipulate bits" "Hack your way to safety" (or whatever makes sense). Maybe end with a sequence where something drastic happens (the player does something and the whole screen changes), fade to black.
I think it'd be useful to show the player what the gameplay is actually like. Sure, it's not for everyone, but you can still show what it is.
