In the field of language technology, researchers are starting to pay more attention to various interactional aspects of language – a development prompted by a confluence of factors, and one which applies equally to the processing of written and spoken language. Notably, the so-called "phatic" aspects of linguistic communication are coming into focus in this work, where linguistic interaction is increasingly recognized as being fundamentally situated. This development resonates well with the concerns of third wave HCI, which involves a shift in focus from stating the requirements on HCI design primarily in terms of "context-free" information flow, to a view where it is recognized that HCI – just like interaction among humans – is indissolubly embedded in complex, shifting contexts. These – together with the different backgrounds and intentions of interaction participants – shape the interaction in ways which are not readily understandable in terms of rational information exchange, but which are nevertheless central aspects of the interaction, and which therefore must be taken into account in HCI design, including its linguistic aspects, forming the focus of this chapter.