userscript.user.js

// ==UserScript==
// @name          SE Chat Fix for Neal
// @author        Robert Lemon 
// @namespace     rlemon.userscript
// @description      Fixes neals buggy ass chat interface
// @include       http://chat.stackexchange.com/rooms/*
// @include       http://chat.stackoverflow.com/rooms/*
// ==/UserScript==

function EmbedCodeOnPage(type, kode) {
    var elm = document.createElement(type);
    elm.textContent = kode;
    document.head.appendChild(elm);
}

function EmbedFunctionOnPageAndExecute(fn) {
    EmbedCodeOnPage("script", "(" + fn.toString() + ")()");
}

EmbedFunctionOnPageAndExecute(function() {
    $('#input').val('');
});