Nice usage of IIFE and comma operator.

Elegant readable solution showing how useful recursion can be.

Nice solution, very readable.

Ain't that a beauty!

Excellent kata.

Regexp as a separator in split, that's magic!

This function doesn't perform complete freeze. Object.keys(object) lists only own enumerable properties, leaving behind the non-enumerable ones. For example:

const o = Object.create(null, {
    prop1: {value:{word:'Hello'}, writable: true, configurable: true, enumerable: true},
    prop2: {value:{word:'World'}, writable: true, configurable: true, enumerable: true},
    prop3: {value:{word:"Don't forget me!"}, writable: true, configurable: true, enumerable: false}, 
});

Object.deepFreeze(o);

o.prop3.word === "Don't forget me!";  --> true
o.prop3.word = "I've been left unfrozen:-(";
o.prop3.word === "I've been left unfrozen:-(";  --> true

Why not?

Nice, looks like efficient code.