We finally managed to get the /vanish command back for you!
This command lets your own player disappear from all others view which can be useful for quite a lot of things (including trolling).
The current implementation basically fakes the player’s death to all other players, making him not appear for them any more. However this comes with a little limitation: Other players can still hear your footsteps if you walk around. Also the effects will currently be reverted when you switch dimension or when you die. You will also be visible to players who connect after you used /vanish as well. It might also be that other players can see you if you used /vanish outside of their range and then come near them (still need to test this – feedback would be appreciated).
However I wanted you be able to use this new feature as soon as possible, which is why it is already included in the newest build. Expect /vanish to improve with the next updates!
PS: /vanish is not merged to 1.8 yet and only available on 1.7.10.