Board Thread:Support Requests - Getting Technical/@comment-24448896-20130527030755/@comment-3335785-20130528095136

Because the chat module is part of the sidebar it is considered a core part of the skin and cannot be modified in the way you're suggesting.

To add extra avatars in would result in a width change, which could disrupt other parts of the page. There are arrows to scroll through however many users are in chat though.