They can read all chat and all whispers. It's really unfortunate because as much as I want to play and build in this game, its just too frustrating knowing I simply MUST use an out of game chat system to not have my information read by devs and guides.
This is a problem because one of my favorite parts about this game was discovering new methods of doing something and having it be my choice whether or not whether I choose to share those methods or perhaps information that no one or very few no about.
Anyways, I just don't see the need for this feature. It just makes people not want to use the in game chat system.
Only problem is, even if you say you will remove guide/dev chat powers, we never know if you truly did. This feature is seriously causing me to not want to play the game at all. And its a shame because its becoming a great game.