Stop sabotaging your Influencers: How language formality undermines engagement in sponsored content

Influencer marketing has rapidly become a cornerstone of modern advertising, yet sponsored posts often underperform compared to organic content in terms of consumer engagement. This study investigates how brand-imposed language constraints affect engagement in sponsored influencer content. Drawing on Media Naturalness Theory and the control paradox, we hypothesize that language formality disrupts the authenticity of influencer communication, leading to lower engagement. Using a dataset of 1.4 million Instagram posts, including around 200,000 sponsored postings, our analysis reveals that formal language reduces engagement, while informal language features, specifically higher use of netspeak and emojis, enhance engagement. To further validate these findings, we conducted a controlled experiment examining the effect of language style on engagement and perceived authenticity. These findings suggest that informal language fosters a more genuine connection between influencers and their audiences, increasing interaction in sponsored content. The paper provides practical recommendations for brands, urging them to co-create flexible language strategies with influencers, allowing for more authentic expression and boosting consumer engagement. The current study also uses the latest agentic AI models to replicate similar results through additional experiments, contributing to the theoretical understanding of influencer marketing and the practical strategies for optimizing influencer collaborations.