Hide or display the lobby chat in the table
When you join a table, both chats are displayed by default (table chat and lobby chat).
Click "Lobby chat" to hide it or display it again.

Sending private messages
If you have a keyboard, you can use the same keyboard shortcuts as the Silverlight version to send privates messages. The usual command is also valid :
/w recipient_name message
You can also touch/click the name of a player, but only in the list (right side of the lobby).
If you have a touch device, the "PM" button provides an easier way to select a recipent :

This button displays the following dialog box :

Enter the name of the recipient in the input area. This box uses autocompletion, so normally you should'nt need to enter the full name.

After validation, the input area of the chat is automatically filled with the PM command and the name of the recipient, you have just to enter your message :

The dropdown under the text box allows to select any player with whom you have exchanged private messages previously (as sender or recipient).
For instance, if you have sent a PM to Duschmoll and received another PM from Patatruc, the dropdown shows both names :

The name of the last sender or recipient is selected by default.
Note : presently, this dialog box doesn't work as expected in Firefox Mobile.