Well, consider the danger of that... you'd reply everytime someone typed something...
<User> Hi
<You> *away
<User> Darn
<You> *away
<User> Stop!
<You> *away
You could put a timer to prevent more than one response every X seconds, but even that would be a problem. You're better off only doing a response to text if your nick is in it...
<User> Hey, You!
<You> *away