Below are commands you can issue in the chat window.
Any arguments go after the command (for example '/whisper arellakirstar hello!' arellakirstar is the target, and hello is the message).
Commands must be prefaced by a / to be activated.

Command

Arguments

Result

Allowall

None

Allows all players to whisper to you

Channel / Chan

(target channel)

Change to a given target channel (1-8 valid options, 8 only if you have a palantir)

Help

None

Displays an in game help menu for emots

Ignore

(target)

Blocks chat text from target account, if a player name is given their account is used.

Ignorelist

None

Lists which accounts you currently have ignored

Ignoreall

None

Blocks all whispers sent to you

NoServer

None

Disables Server Announcements

Ping

None

Sends a ping packet to the client and prints out the delay in msec of a reply. Currently only available in the beta client

Reply

(message)

Sends a whisper to the last person who sent one to you

Unignore

(target)

Removes target from your ignore list

W

(message)

Sends a whisper to the last person you sent one to.

Whisper

(target) (message)

Sends a privatemessage to a given target.