We explored the role of social norms by analyzing Twitter data gathered through the Covid19 Infodemics Observatory, an online platform developed to study the relationship between the evolution of the COVID-19 epidemic and the information dynamics on social media. Our findings suggest that the structural basis of online communication network (e.g., those based on content sharing) can promote the emergence of norms misperceptions (e.g., pluralistic ignorance) in fake news spreading. This study can help tailoring future interventions to curb misinformation and inform further research addressing norms in AI systems through theoretical modelling and social simulations.