I didn't do it entirely by hand, but I didn't just one-shot it with AI either (good luck). Instead, I wrote the whole dialogue in a special format specifying alternate words [like|similar to] [this|what I'm [currently doing here|doing right now]]. For each length-200 block, the number of variations grows exponentially in the number of "options" to thus choose from, so it becomes feasible to have a computer systematically choose options so as to hide the desired secrets.
The same method could be used for monospace alignment, though I suspect it would be harder the narrower the page be.