When entering a new message everything is lost after a session timeout. It would be nice to keep such texts for a while and restore them like a postponed message in other clients. Technically it could be done with a small database (maybe sqlite) which holds the last session-ID for each user. When a HTTP/POST with a new message reaches the server with an invalid Session-ID, this ID is searched in the database. The message text then is saved in the DB for this user. When the user creates a new message, the saved text will be sent in the textarea.
Another technical approach would be a keep alive using Ajax-technology.
We have some users that would really appreciate this feature.