The occupational landscape of the digital economy is rapidly changing, resulting in the emergence of multidisciplinary occupations. Emerging occupations such as user experience (UX) design are in high demand, but these occupations lack clear boundaries and have yet to develop into a profession with a specified, coherent body of knowledge. While traditional occupations such as medicine and law successfully claimed their professional jurisdiction and high social power and status long before the Internet, how do these emerging occupations work towards professionalization, particularly as they are increasingly supported by and through online communities? In this paper, we investigate an online UX community to understand how UX practitioners specify their occupational knowledge and professional boundaries. Using this case as an example and provocation, we discuss how online communities support the emergence of new occupations and may play an indispensable role in modern day patterns of professionalization.