Sorry, but I have a hard time getting online on weekends.
Anyway, I have an answer for you. It is the SpecialEvent actor that does it. In any state other than "None" (in the Object menu), the actor will display the message when it's triggered, even when it's playing sounds, damaging pawns, etc. However, there are two ways that a SpecialEvent actor can display its message. If bBroadcast is false in the SpecialEvent's properties, then the message goes to the speech window, and only the player that triggered it will see it. If bBroadcast is True, then the message is displayed in the middle of the screen, all players will receive it, and they will hear a message beep.
As far as TranslatorEvent messages go, the player does need to have a Translator to read them. Triggering one of these will cause it to display the next message in that actor (a TranslatorEvent actor can hold up to 3 messages).