Don't forget to turn it off.
If you're binding a key to +taunt, it means that when you press that key, the system believes that the button that does taunt is being pressed down. It doesn't understand that that key is released until it receives the -taunt command. I discovered this when I was setting up a taunt key bind last night, and have since seen it all over these forums today.
Therefore, the better taunt key bind would be (say you're binding to key 't'):
bind t +taunt;-taunt
That way, when you press and release t, it does the taunt once, rather than continuously.