Speakers often mitigate by downgrading their own role in their utterances, depersonalizing the origin of their utterances and de-focalizing the deictic-personal point of reference (Briz, 1998; Caffi, 2007). Linguistically, this can be accomplished by means of impersonalization, generalization and referencing general knowledge. Interestingly, using expressions that suggest the objective, general or shared status of information can, in some cases, lead to argumentative reinforcement or boosting11Terms ‘strengthening’, ‘boosting’ and ‘reinforcement’ are used when describing pragmatic effect of intensification. (Cornillie, 2007a, b; Caffi, 1999; Briz, 2016).Our goal is to examine the relationship between the functions of mitigation and reinforcement in indirect evidential expressions of common knowledge and folklore. With these types of expressions, the indirect nature of the source of knowledge triggers the mitigating function, while highly intersubjective and shared evidence can, in parallel, boost the strength of the argumentation or reinforce the interpersonal relationships in interactive contexts.In addition to revising the theoretical field related to mitigation, reinforcement and indirect evidentiality, we will discuss the function of say-constructions based on the analysis of several oral corpora in two languages: Spanish and Polish.