Yes, that's one of the things that really should have been an extension. Tree Style Tab works alright as an extension-provided sidebar.
Putting the chat or sidebar in the core of the browser sounds very much like something done by a developer who wasn't around for Mozilla prior to Firefox, and isn't aware of the original goal of being the antithesis of the browser that included everything and the kitchen sink.
Putting the chat or sidebar in the core of the browser sounds very much like something done by a developer who wasn't around for Mozilla prior to Firefox, and isn't aware of the original goal of being the antithesis of the browser that included everything and the kitchen sink.