You're right – I guess I got too hung up on the types. What I meant to say is that I prefer to distinguish "`a` is not equal to `b`" and "equality between `a` and `b` is undefined"; the typing aspect is kind of orthogonal and muddles the discussion.

(I guess I ended up conflating equality and equivalence[1], but in my defense, most languages seem to do that too; and the presence of the `is` operator in Python mixes things up even more)

[1] https://en.m.wikipedia.org/wiki/Equality_(mathematics)#Relat...