Why do some states possess more leverage to diffuse norms than others? In the case of competing interpretations, what makes one translation strategy more successful over another? Although it is often assumed that norm translation simply "happens" through the interaction of political and cultural systems, we argue that individuals and institutional flexibility play a crucial role in the success and failure of norm diffusion. Analyzing the contending interpretation and diffusion of the Common but Differentiated Responsibilities norm between AILAC and ASEAN countries within the UNFCCC, we illustrate how the use of informal negotiation platforms and the skills, mandates and connections of their negotiators played a crucial role in the respective success and failure of their normative diffusion. AILAC countries have understood CBDR in its "Paris" version inclusive of voluntary pledges, high level of legalization and as a venue for economic growth. ASEAN, to the contrary, remained tied to the "Kyoto" version of CBDR, based on historical responsibilities and low level of legalization. While the more flexible and ad-hoc AILAC was able to effectively diffuse its interpretation of CBDR into the climate regime, the strictly intergovernmental ASEAN was unable to do the same. These findings advance the literature on norm entrepreneurs from Global South and confirm several assumptions of the Informal Institutions theory. They also show, however, the importance of individuals as a defining condition of both norm entrepreneurship and the functioning of informal institutional platforms.