If it is text on screen then its almost certainly keybound text, ie:
In quake 3 there used to be set map areas such as Lower Hall, Main courtyard etc and could be displayed by somehing like %M or similar. People would maybe bind "Enemy Spotted in %M need assistance" to a mouse or keyboard button.
In counter strike we had no such feature so we had a LOT of messages bound.
Of course they may just be fast typers, but not likely.
Out of curio any game in particular you are refering too?