I agree with all of that, but I don't see what it has to do with this thread of the discussion.

The comment I replied to was wondering what exactly greener_grass was referring to when they said:

> outside of Functional Programming […] How can you "Make illegal states unrepresentable" with mutable state and sequences of mutations that cannot be enforced with the type system?

And my guess was that they had illegal transitions between states in mind. Those are hard/impossible to statically reason about when the program is written as "sequences of mutations" (particularly when aliasing is possible).