From Lost Hope Manual
a. Chat Usage
Click in the black box after your name and typing in the message followed by pressing enter or clicking 'Say' will send your message. You may not see it at first, because chat refreshes once every 5 seconds.
b. Chat Syntax
For a normal message, just type in what you wish to say, and press enter. If you wish to do an emote, type a colon : before your message such as ": likes to eat food". If you want to private message someone, either click on their name in chat, or type "/w name, message" name being the player's name and message being the message you wish to send to that person. Ignoring other players can also be done by typing "/i name," to hear a person again type "/h name," and to list all the people you are currently ignoring, type "/li" -- note that you cannot ignore moderators. To send a sales message, type "/s " before your message. Private messages are kept even if the recipient is not online at the time. They get deleted on reading
c. Chat Types
There are three different chat rooms. First is the default regular chat. Second is the SalesChat where all messages are sent as emotes. Third is ClanChat where you can talk to only the people in your clan. When you click on the type of chat you want, wait 5 seconds before thinking something is wrong, because chat refreshes every 5 seconds.
The command to use the calculator that is built within chat is /calc. You may use any of the symbols [0-9]+*-/.()^ and space to form arithmetical constructs in the usual way. The expressions are evaluated with multiplication (*,/) having higher priority than addition (+,-). The ^-symbol stands for the power function and is written in binary prefix notation, so ^(2,3) means 2 to the pwoer of 3 and the result is 8.
To memorite a text, you simply write /memo in front of the text. To display the memorized text later, just type /memo.
Furthermore there are: /sta (beast), /shr (shrine), /skc (kills), /gem (stones given to Joe) and /cjc (JC status).
For a complete list see: Chat Commands