Beep boop. I've made a greasemonkey script in the meantime.
// ==UserScript==
// @name Confirm Navigation on gdnet Chat
// @namespace fastcall22.com
// @include http://www.gamedev.net/chat/*
// @version 1.0
// @grant none
// ==/UserScript==
(function(){
window.addEventListener('beforeunload',function (e){
return ((e||window.event).returnValue) = 'You are about to leave the chat.'
})
})();
It's surprising how often you can accidentally leave the page from just the keyboard... alt+home, alt+backspace, backspace, ...