By user request, the Howls Of Outrage Greasemonkey script for Metafilter, which shows a popup window of all users who have favorited a post or comment on mouse hover, is updated to version 4.2. The download link is sited on my original devoresoftware.com domain, because the userscripts.org Greasemonkey scripts repository has been down or very unreliable for many months.
Previous version of the script, using the latest versions of Greasemonkey and the Firefox browser, were unable to get past the "loading…" part of the popup box. This was due to permission problems with the GM_xmlhttpRequest function, at least while running Firefox under Windows 7. Curiously, a Mac using the latest Firefox with script version 4.1 still worked OK. Regardless, the Howls Of Outrage script should work for all supported Firefox platforms now.
If you use the Chrome browser and read the Metafilter site, I recommend installing the Howls Of Outrage extension from the Chrome Web Store.