Online Community Engagement, Social Acceptance, and Planning Legitimacy: Responses to Urban Development Priorities in Municipal Facebook Comments from Constanța, Romania

Public administrations increasingly use social media to communicate urban-planning decisions, creating observable spaces in which platform-engaged users express criticism, support, proposals, local knowledge, and evaluations of public authorities. Because such comments are self-selected and platform-specific, they cannot be treated as representative measures of city-wide public opinion. This study examines 3228 Facebook comment records associated with 82 posts published by the Municipality of Constanța, Romania, on mobility and transport, planning instruments and regulation, and public space and regeneration between 2016 and 2026. Using computationally assisted and manually supervised content analysis, the study distinguishes three complementary dimensions: comment-level social acceptance, modes of online community engagement, and planning legitimacy. Opposition accounted for 49.7% of comments, compared with 11.6% acceptance, while proposals or suggestions represented the most frequent participation mode (23.9%). Trust, corruption, and institutional credibility emerged as the dominant legitimacy frame (59.1%), followed by environmental and green value (44.4%), mobility and traffic (32.7%), and performance and feasibility (23.5%). All three policy domains recorded negative corpus-level Social Acceptance Index values, with the strongest opposition concerning planning instruments and regulation (−0.427). Within this bounded Facebook environment, the findings show that critical responses cannot be understood solely as rejection of urban interventions, because the corpus also contains substantive planning-relevant contributions and distinct claims about institutional and planning legitimacy.