Storing an IR also means we can create languages beyond the limits of syntactical practicality. Imagine, for example, an entire comment/documentation dimension of the code. Instead of commenting on a line near some code, you could attach comments semantically to an expression, or to a variable, or to any unit of code.

Token, statement and block level annotations would actually be nice. Perhaps even nicer if those annotations could be structured data instead of just text. You could create a truly self-describing code base without having to worry too much about the second hardest problem in programming.