You cannot disable emoticons in chat rooms that are hosted on a Microsoft Office Communications Server 2007 R2, Group Chat server.
To resolve this issue, install the following cumulative update:
2491973 Update package for Office Communications Server 2007 R2 Group Chat server: March, 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
After you apply this update package, you can configure the Office Communications Server 2007 R2, Group Chat server to disable emoticons in chat rooms, or you can do it by using Group Policy object (GPO).