People benefit from high-quality supportive messages online, yet the production of these messages is a complex process that is shaped by multiple factors. As informed by the lens model, this study seeks to investigate the interplay of third party's supportive messages as a form of behavioral residue and the support seeker's seeking strategy as an identity claim on providers' language use in supportive messages conveyed in public and private channels online. Data showed that providers' use of words that differentiate supportive messages of varying quality (i.e., first-person singular pronouns, second-person pronouns, social process words, cognitive process words, and anxiety words) was influenced by the quality and quantity of others' comments, the support-seeking strategy, and the publicness of the communication channel in an interactive way. Findings extend the literature by providing a more comprehensive account of online supportive communication and illuminating the actual language used to support others. Lay Summary People benefit from receiving high-quality social support online. Research has identified first-person singular pronouns, second-person pronouns, social process words, cognitive process words, and anxiety words as linguistic components that differentiate supportive messages of varying quality. This experimental study explores how exposure to a support seeker's seeking post and supportive messages from third parties influences language use in public and private support provision. In this experiment, we manipulated the quality and quantity of third parties' supportive comments, the support seeker's tendency to approach or avoid the stressor in their support-seeking message, and the publicness of the communication channel used to provide support. Results showed that when exposed to a small number of comments from others, prospective support providers used less supportive language (i.e., more first-person pronouns and less anxiety words) as the quality of others' comments increased. Providers who viewed approach-oriented seeking messages used more anxiety words but less cognitive process words. In addition, support-seeking strategies moderated the effect of the quality and quantity of others' comments on providers' language use. Channel publicness reduced providers' use of social process words and moderated the effect of support-seeking strategies on the use of pronouns.
