This paper deals with the question in how far pragmatic and discourse conditions affect the communicative construction of collective knowledge. Research in Discourse Semantics predominantly deals with corpora consisting of mass media texts. In doing so, knowledge that becomes manifest in these texts can be identified and substantially described. However, to what extend this knowledge is also used as a pragmatic-interactive resource in other communicative contexts and in social media communication cannot be explored. This paper aims at reducing this research desideratum by analyzing a different type of data (realisations in internet forums), using the example of internet forums dealing with the topic of OSTDEUTSCH (East German). Following discourse pragmatic procedures exemplary data will be discussed in order to reveal which pragmatic conditions are essential and for what interactive reasons discourse knowledge is used as a communicative resource by the participants in the forum. There will be a focus on the essential condition of interactionality and on interferences between realizations of discourse in mass media and in internet forums.