From ES6 section, first thing I notice:

> let is the new var. Constants work just like let, but can’t be reassigned. See: Let and const

I say it once, I say it one thousand times: "Let is not the new Var".

They certainly have some similar behaviors but surely they do communicate very different things to a developer who is reading the code.

let: "you shouldn't/can't edit outside this block scope"

var: "feel free to change me whenever you want inside this scope (whether it's global or function)

JS stuff aside, this is actually very helpful.