Ticket MC-797 was closed as resolved (along with many others as dups), but this is issue is definitely not resolved!

From the multiplayer server console:

Kill command is listed in the help:

help 3
...
2013-02-09 19:22:24 [INFO] --- Showing help page 3 of 5 (/help <page>) ---
2013-02-09 19:22:24 [INFO] /kill
...

Let's try the command:

/kill
2013-02-09 19:22:27 [INFO] You must specify which player you wish to perform this action on.

Okay, let's try specifying a user:

/kill kiloforce
2013-02-09 19:22:34 [INFO] You must specify which player you wish to perform this action on.

Found on both the 1.4.7 and 13w06a snapshots.

So either the kill command needs to be fixed (preferred), or it should be removed from the server console commands.