As far as I know, this has never been done, by UltraHal or any other chatbot. Typically, Facebook chatbots are either Facebook Apps or Facebook Chat, as in instant messaging in the little window. For any bot to interact properly with Facebook, a complete set API functions, mirroring the functions available to human users, would be necessary. I haven't spent much time on the Facebook API lately, but assume it's still a limited subset. The only other way I can think of would be to automate browser macros, using browser testing software, and marry that to the chatbot. For me both Apps and Chat are a fail, because as you point out the real challenge is to emulate human usage, which includes proactive status updates as well as in-page reactive comments, not to mention PMs.
The real frontier for social bots is not Facebook, but Twitter....
