Okay, so most of this just includes jQuery.
I read about GM_setValue and getValue, but I don't know how to call them from the page, or if I should allow it via unsafeWindow.
I would quite like to add a "show" and a "hide" button, but I don't know how to do that without using unsafeWindow to call setValue to save the list of users.
It'd just make it more convenient.
Cheers

// ==UserScript==
// @name phpbb3_user_ignore
// @namespace none.exists.here
// @description Ignore users on phpbb3
// @include *.blizzhackers.cc/viewtopic.php?*
// @include blizzhackers.cc/viewtopic.php?*
// ==/UserScript==
var $;
// Add jQuery from http://joanpiedra.com/jquery/greasemonkey/
(function(){
if (typeof unsafeWindow.jQuery == 'undefined') {
var GM_Head = document.getElementsByTagName('head')[0] || document.documentElement,
GM_JQ = document.createElement('script');
GM_JQ.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js';
GM_JQ.type = 'text/javascript';
GM_JQ.async = true;
GM_Head.insertBefore(GM_JQ, GM_Head.firstChild);
}
GM_wait();
})();
// Check if jQuery's loaded
function GM_wait() {
if (typeof unsafeWindow.jQuery == 'undefined') {
window.setTimeout(GM_wait, 100);
} else {
$ = unsafeWindow.jQuery.noConflict(true);
letsJQuery();
}
}
// All your GM code must be inside this function
function letsJQuery() {
var temp;
var user_count = GM_getValue('user_count');
var users = new Array(
'user1',
'user2'
);
$('.postauthor').each( function() {
t = $(this).html();
index = $.inArray(t, users); // Returns index, or -1
if( index > -1 )
{
$(this).parent().parent().next().css({'display' : 'none', 'height' : '0'});
// hide and show "show"
} else {
// show "hide" button
}
});
}