Information and Communication Technologies (ICT) are often considered as a vehicle for innovation in citizen participation and collective action. Indeed, while the renewal of representative democracy is long in coming, the actual changes appear to be at the margins of official political processes. By analyzing and comparing a corpus of digital debates hosted by the Discord community supporting the French political party La France Insoumise, this chapter focuses on the emergence of new forms of political engagement and mobilization. The meeting point between this ‘digital third place’ and the activist sphere contributes to reshaping partisan practices, the development of activist expertise and, in general terms, the forms of organization and coordination of collective action. The Discord of ‘the rebellious’ (‘insoumis’ in French) appears to be an autonomous space, relying on engaged information and communication practices and fostering recognition and appreciation of peripheral political activities. Its innovative effect is mostly associated with its liminal location: as a specific part of the wider galaxy of the ‘protest internet’, the community is torn between the new forms of ‘informational mobilization’ and the traditional forms of political activism. In the end, the new politicized communication practices contribute to moving the boundaries of politics and political engagement as well as those of the public sphere reconfigured by the new fragmentation and creation processes of on-line critical publics. Moreover, to understand the distinctive form of this Discord Community, its main characteristics will be compared with another on-line critical public: Beppe Grillo’s Five Star Movement (M5S) in Italy. Links will be drawn to our previous work on the on-line activism within this movement, which will lead to a discussion on the permanent tension between (re)centralization and autonomy which links on-line publics and party leaderships.