in general: highlights are like warnings that are triggerd by events, like an alarm clock.
here it means that everytime, a selection of words is used in the chat, those words will be displayed in a different color.
this way you can see more easy when someone wants your attention.
@alebrije: the whole point of the community edition is to implement stuff, eihrul is too stubborn to. I personally don't expect another release of sauerbraten.