MoronSilencer.js

// ==UserScript==
// @name         MoronSilencer
// @version    1
// @grant        none
// @match                http://www.cplusplus.com/forum/*
// ==/UserScript==
console.log('MoronSilencer is working its magic');

var morons = [ /*write the name of your morons here*/ ];

function map(xs, f){
    var ret = [];
    for (var i = 0; i < xs.length; i++)
        ret.push(f(xs[i]));
    return ret;
}

function get_post_node(node){
    while (node.className != 'C_forPost')
        node = node.parentNode;
    return node;
}

function remove_moronic_posts(){
    var whos = document.getElementsByClassName('dwho');
    var l = whos.length;
    var list = map(morons, x => '/user/' + x + '/');
    for (var i = 0; i < l;){
        var who = whos[i];
        if (!who){
            i++;
            continue;
        }
        if (!who.firstChild.getAttribute){
            i++;
            continue;
        }
        var name = who.firstChild.getAttribute('href');
        if (list.indexOf(name) < 0){
            i++;
            continue;
        }
        get_post_node(who).remove();
        l--;
    }
}

function remove_moronic_post_previews(){
    var auths = document.getElementsByClassName('auth');
    var l = auths.length;
    var list = map(morons, x => '(by ' + x + ')');
    for (var i = 0; i < l;){
        var auth = auths[i];
        var name = auth.innerHTML;
        if (list.indexOf(name) < 0){
            i++;
            continue;
        }
        auth.parentNode.innerHTML = 'something moronic some moron said';
        l--;
    }
}

remove_moronic_posts();
remove_moronic_post_previews();

I'm curious as to why you implemented your own map function instead of using the one JS provides. (Array.prototype.map, https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map)

Because I didn't know about it. I hack C++, not JS.

Fair enough.