https://greasyfork.org/en/scripts/434552-r-forsen-emotes-for-old-reddit/code

(function () {
        // 5317 = forsenE
        // 5318 = gachiBass
        // 5319 = forsenDespair
        // 5320 = forsenBased
        // 5321 = OMEGALUL
        // 5322 = megaLUL
        // 5323 = forsenCope / Copesen
        // 5324 = PagMan
        // 5325 = Sadeg
        // 5326 = forsenCD
        // 5327 = BatChest
        // 5330 = :tf: / Trollface
        // 5331 = Clueless
        // 5332 = monkaOMEGA
        // 5333 = WutFace
        // 5334 = cmonBruh
        // 5335 = pepeLaugh
        // 5336 = FeelsOkayMan
        // 5359 = forsen as doc
        // 5360 = LULE

        var emotes = {
          ":5317:": "https://reddit-econ-prod-assets-permanent.s3.amazonaws.com/asset-manager/t5_33td5/AT7s0VNX3k.png",
          ":5323:": "https://reddit-econ-prod-assets-permanent.s3.amazonaws.com/asset-manager/t5_33td5/35Audg7pV4.png",
          "emote_key": "image_link" // add your emotes here
        };
        var emoteMatcher = Object.keys(emotes).join('|');

        var emoteSize = 20; //change these if you want the emotes to be bigger or smaller, it's 20 on new reddit so i just used that

        Array.from(document.getElementsByTagName("p")).forEach(function (elem) {
            var html = elem.innerHTML;
            var emoteMatches = html.match(new RegExp(emoteMatcher, 'g'));
            if (emoteMatches) {
                emoteMatches.forEach(function (possibleEmote) {
                    if (emotes.hasOwnProperty(possibleEmote))
                        html = html.replace(possibleEmote, `<img src="${emotes[possibleEmote]}" width="${emoteSize} height="${emoteSize}">`);
                });
                elem.innerHTML = html;
            }
        });
    })();