That was the right tradeoff for the situation. I think any attempt to use this case study to draw conclusions about maintainability would be a mistake; that's just not what this is useful for.
(To be clear, the optional portions in which I implement SSA, various optimizations, a Hack-style allocator and some ad-hoc codegen is much less readable.)
It sounds like you and your classmates are top notch and will go on to some pretty freaking cool careers (ex: I'd work at Jane Street if I was not a parent and a lot smarter :)). Out of curiosity, what are the typical places your classmates go upon graduation?