The OpenInv plugin (forums.bukkit.org/threads/15379/) has a feature where you can open chests silently. According to the forum post, "Silent opening of chest, no sound and opening animation".

This should be included in VanishNoPacket, so vanished players do not trigger the opening animation/sound when opening a chest.

Duplicate of #41

OpenInv does some dirty reflection stuff that I don't wish to bring into this plugin. It would result in forcing users to constantly update, which is something I no longer have to worry about with 3.0