I imagine it was the cvar that dictates how long (in milliseconds) a message is displayed on screen. With that hot fact in hand, you can probably figure out what its actual name is by doing /cvarlist (or /cvarlist cg_, probably, if you use the MBII Client) and perusing. I don't remember the name.
There's also the option in settings for turning off all-chat (but keeping team chat), which is usually effective if you're trying to blot out the in-game banter.