redesign_expand_on_scroll.user.js

// ==UserScript==
// @name         reddit expand on scroll
// @version      0.4
// @require      https://raw.githubusercontent.com/vvo/in-viewport/46aa0be7cb688613213b16693d4501b61071d45e/build/in-viewport.min.js
// @author       Creesch
// @match        https://new.reddit.com/*
// @grant        none
// @run-at document-end
// ==/UserScript==



(function() {
    'use strict';

    function visible(expando) {
        window.requestAnimationFrame(function() {
            expando.click();
        });
    }

    // Function to handle incoming events.
    function handleEvent(e) {
        if(e.detail.type === 'post') {
            const post = e.target.closest('.Post');
            const expando = post.querySelector('button[data-click-id="expando_open"]');
            if(expando) {
                inViewport(expando, {
                    offset: 300
                }, visible);
            }

        }

    }

    // Ready the event listener
    document.addEventListener('reddit', handleEvent, true);

    // Let reddit know you are ready
    const data = {
        name: 'expand-all', // optional
    };
    const event = new CustomEvent('reddit.ready', { detail: data });

    document.dispatchEvent(event);
})();