Resaltar comentarios de usuarios recientes en Menéame

// ==UserScript==
// @name        meneame.net - Destacar comentarios de usuarios recientes
// @namespace    http://tampermonkey.net/
// @version     1.0
// @description Destaca los comentarios de aquellos usuarios creados hace menos de 90 días.
// @author      Niko
// @match       *://*.meneame.net/*
// @grant       GM.setValue
// @grant       GM.getValue
// ==/UserScript==

/*jshint esversion: 6 */

// ---- SCRIPT CONFIG ----
const NOOB_DAYS = 90;
const BGPLAIN_COLOR = '#EEE';
const BG_STRIPES_COLOR1 = '#fff';
const BG_STRIPES_COLOR2 = '#fff5ed';
const STYLE = "STRIPES"; // PLAIN or STRIPES

// ---- API values ----
const USERNAME_CLASS = '.username';
const REQUEST_URL = 'https://www.meneame.net/backend/get_user_info?id=';

window.onload = function () {
    let usernames = document.querySelectorAll(USERNAME_CLASS);
    usernames.forEach( function(node) {
        processUserNode(node);
    });
};

function processUserNode(node) {
    const user = node.textContent;
    (async () => {
        let date = await GM.getValue(user, "");
        if (date === "") {
            requestRegistrationDate(node, user);
        } else {
            checkIfNoobUser(node, date);
        }
    })();
}

function requestRegistrationDate(node, user) {
    let xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState === 4 && this.status === 200) {
            const dateRegex = /((0[1-9]|[12]\d|3[01])-(0[1-9]|1[0-2])-[12]\d{3})/;
            const date = this.responseText.match(dateRegex);
            GM.setValue(user, date[0]);
            checkIfNoobUser(node, date[0]);
        }
    };
    xhttp.open("GET", REQUEST_URL + user, true);
    xhttp.send();
}

function checkIfNoobUser(node, dateStr) {
    const dateArray = dateStr.toString().split('-');
    const date = new Date(dateArray[2], dateArray[1] - 1, dateArray[0]);
    const daysSinceRegistration = (Date.now() - date.getTime()) / 3600000 / 24;
    if (daysSinceRegistration < NOOB_DAYS) {
        highlightUser(node);
    }
}

function highlightUser(node) {
    switch(STYLE) {
        case "PLAIN":
            node.parentNode.parentNode.style.backgroundColor = BGPLAIN_COLOR;
            break;
        case "STRIPES":
            const BGSTRIPES = "repeating-linear-gradient( 45deg, " + BG_STRIPES_COLOR1 + ", " + BG_STRIPES_COLOR1 + " 10px, " + BG_STRIPES_COLOR2 + " 10px, " + BG_STRIPES_COLOR2 + " 20px );";
            node.parentNode.parentNode.setAttribute("style", "background-image: " + BGSTRIPES);
            break;
    }
}