Removes comments with ads in signature on the https://bitcointalk.org forum.

bitcointalk-poor-comment-blocker.user.js

// ==UserScript==
// @name           BitcoinTalk Poor Comment Blocker
// @version        1.0
// @author         CapnSparrow@BitcoinTalk
// @description    Removes comments with ads in signature on the https://bitcointalk.org forum.
// @include        https://bitcointalk.org/index.php?topic=*
// @require        https://code.jquery.com/jquery-3.3.1.min.js
// @run-at         document-end
// ==/UserScript==

// Configuration.
//============================================================================
/*
 * Define block words here. Each item is a regex. Case is ignored.
 */
var blockWords = [
    "telegram"
    , "whitepaper"
    , "discount"
    , "\\bjoin\\b"
    , "be part of"
    , "pre-?sale"
    , "\\bico\\b"
    , "token"
    , "empower"
    , "casino"
    , "fortune"
    , "\\bdice\\b"
];

/*
 * We won't block these phrases. Each item is a regex. Case is ignored.
 */
var exceptionalWords = [
    "HoweyCoins" // Not a real ICO but a joke. See https://bitcointalk.org/index.php?topic=3920469.0
];

/*
 * If a user has more than this number of merits we will never block him/her in any case.
 */
var minMeritsToBypassBlocking = 1000;
//============================================================================

blockWords = new RegExp(blockWords.join("|"), "i");
exceptionalWords = new RegExp(exceptionalWords.join("|"), "ig");

$(".signature").each(function () {
    var $this = $(this);

    // Fetch number of merits.
    var match = /merit:\s*(\d+)/i.exec($this.parents("td.windowbg, td.windowbg2").find(".poster_info").text());
    var meritsCount = match[1];

    var signatureContent = $this.html();

    // Clean up.
    signatureContent = signatureContent.replace(exceptionalWords, "");

    if (meritsCount < minMeritsToBypassBlocking && blockWords.test(signatureContent)) {
        hidePost($this);
    }
});

insertCss(
    ".hidden-post-container {"
        + "background-color: #ECEDF3;"
    + "}"
    + ".hidden-post-inner {"
        + "opacity: 0.05;"
        + "transition: 0.2s opacity;"
    + "}"
    + ".hidden-post-inner:hover {"
        + "opacity: 1;"
        + "transition-delay: 0.5s;"
    + "}"
);

function hidePost($signature) {
    $signature.parents("td.windowbg, td.windowbg2").addClass("hidden-post-inner").parent().addClass("hidden-post-container");
}

function insertCss(css) {
    var style = document.createElement("style");
    style.type = "text/css";
    style.innerHTML = css;
    document.head.appendChild(style);
}

Whitelisting would be a helpful feauture. It can be stored in the browser offline. There is such an implementation here:

https://github.com/Tiramisu77/Bitcointalk-Post-Filter/blob/d4442f635099692a294b916d27a2ec6c509fe5d3/Bitcointalk-Post-Filter.user.js