If enough users mute a thread, it becomes globally muted for all members. It's a good tool if used properly, but people have obviously started abusing it. The web team is currently working on a fix for it. You can read Deej's post [url=http://www.bungie.net/7_Global-Mutes-the-Moderation-System-and-you/en/Forum/Post?id=62754532]here.[/url]