The big question that pervades debate between techno-optimists and their detractors is whether social media are good for democracy. Do they help to produce or accelerate democratic change or, alternatively, might they hinder it? This article foregrounds an alternative perspective, arguing that individual social networking applications likely do not fulfil a single political function across national contexts. Their functionality may be mediated instead by language and by pre-existing relationships between the state and offline domestic media. We arrive at this conclusion through examining reactions on Twitter to two fatal events that occurred in early 2015: the death in suspicious and politically charged circumstances of the special prosecutor Alberto Nisman in Argentina, and the murder in Russia of opposition activist Boris Nemtsov. Several similarities between the two deaths facilitate a comparative analysis of the discourses around them in the Spanish-language and Russian-language Twitter spheres respectively. In Russia, a hostile social media environment polluted by high levels of automated content and other spam reduced the utility of Twitter for opposition voices working against an increasingly authoritarian state. In Argentina, a third-wave democracy, Twitter discourses appeared as predominantly coextensive with other pro-government and opposition online, print, and broadcast fora, thus consolidating and amplifying a highly polarized and repetitive wider public political conversation. Despite the potential for social media to help citizens circumvent restrictions to discursive participation in national public spheres, in both cases compared here language environment and domestic political structures contribute significantly to determining the uses and limitations of online spaces for expressing opinion on current affairs stories involving the state.