According to Jeff and Marc's comments on this answer, being on a chatroom's whitelist is no longer a guarantee that a user may talk in the room. Users must also meet the chat system's required minimum rep for talking — currently 20 — except for a brief window.
However, the "access" tab of room info pages in chat still reads
Regardless of the room's general access setting and their reputation, these users will be able to talk in this room.
(emphasis mine). This should be modified to describe the new settings.