In this paper, I argue that it is necessary to take into account rhetorical and praxeological relations in order to adequately describe not only the functions of non-verbal constituents or the relations between exchanges in service encounters, but also the specific features of parenthetical constituents, which have hitherto withstood syntactic or textual analyses. I also show how a modular approach to discourse complexity allows us to describe some problematic constructions without resorting to ad hoc solutions, by using and combining categories that have been independently motivated in the model.