Objection: Lets say somebody is trying to give out their MSN to a non + user. Now they want to repeat their MSN email thingy a few times in 6 second spurts so the non-plus user can get the email address correctly. Now if this message can't get through because the server is playing a CTF game, and the person can't repeat it for a while, wouldn't that be quite inconvenient? That is why JJ2+ has the pressing up to repeat the last chatline option and also you can press ctrl+V in the chatbox to paste chat. This is there to make it easier. But what you're suggesting defeats the whole purpose. There are many reasons why a line would want to be repeated.

Also, JJ2+ has chat-flood control. If a line is repeated over and over too many times, it kicks the player and if it continues, the player then becomes banned.