The formulation and placement of Spanish personal pronouns is a traditional topic of research on syntactic variation that has not yet received a comprehensive explanation. The present study focuses on expressed yo ‘I’ as a communicative choice in a corpus of readers’ comments on digital news texts. The first-person pronoun is approached as an element that explicitly anchors discourse in the viewpoint of the speaker, thereby specifying the cognitive domain in which the content is to be interpreted. A distinction is proposed between epistemic contexts, where either a personal stance or behavior is described, and epistemic-evidential ones, aimed at lending support to argumentation based either on personal witnessing or on life experience. Variation between the preverbal and postverbal placement of the pronoun is found to correlate with the different contextual types. Evidential uses exhibit very high frequencies of preverbal yo, in line with the self-attributed authority of the speaker. Conversely, the postverbal pronoun, while still entailing the construction of their viewpoint into discourse, signals the fact that such viewpoint is not the dominant one. This can explain the association of this variant with epistemic contexts where predefined, often hypothetical situations are described. It is concluded that the development of a model based on the construction and interpretation of discourse viewpoint can be very beneficial in advancing knowledge of pronoun variation.