Companies commonly implement knowledge-sharing platforms to promote informal learning in the workplace. These platforms can suffer from lack of use. Enterprise social media (ESM) are other means of communication that are increasingly proposed to workers as a frame for collaboration and knowledge sharing. They nevertheless present risks of misuse that may threaten both effective learning and enterprises’ return on investment. In this paper, we discuss the principles and features of social media and present to what extent they promote informal learning in the workplace. We then propose to implement, in a real context, a user-centred design methodology to 1) extend a traditional knowledge-sharing tool with social features; and 2) show how these social features can be adapted to match the needs of workers and give them a more propitious and sustainable learning environment. Outcomes of the implementation in a real context show that: 1) added social functionalities promote workers’ participation, visibility, reputation and group awareness; 2) applying a user-centred approach to the design of the tool showed a specific distribution in the management of the different features, according to role distribution in the community of practice: it was perceived by workers as a guarantee of better use of the social features; and 3) adding reflexive indicators gives great potential to the tool to trigger positive intrinsic benefits, positive attitude and continuous use of the learning tool. A first qualitative assessment shows positive results from our design choices in terms of feature usefulness, user satisfaction and benefits in the given context. We are currently working on further evaluation to consolidate and generalize our findings on the value of comments, ratings and reflexive indicators to socialize traditional knowledge-sharing tools and sustain their use for informal learning in the workplace.