Provide an API hook to extension developers which notifies on each received message before it is going to be distributed to the users.

Bots can only delete already delivered chat messages afterwards. Clients can intercept the deletion. Furthermore it is not possible to write own chat commands for now.

With a hook, if a user types '/do something', extension developers were able to prevent the delivery of the message and perform some action instead.

Beyond that I would like to see API calls to send chat notifications to specific users - just like 'your message has not been sent yet. It will be reviewed by a moderator'.