You can do this with little scripting knowledge , lets say someone wants to script something that says your name. Then he gets to know %client.name , then he tries to change it ... voila his name got changed temporarily.
About talking for someone , real noobs can't really do this but if someone can script some more he will know that servercmd* function can be called then its just a matter of time that he finds out what thefirst argument is , after that he can make any player do anything even if he didn't want to.
I hope this gives an answer to you guys.
I did not mean to learn noobs how to do it but maybe I did.
If you get into a server where this happens, just leave the server.
They'll most likely abuse it more and more because they get better at things.