Leech (2014: 99) identifies claiming common ground with solidarity arguing that it especially serves to reduce the social distance between speakers and promotes what Lakoff (1973) calls camaraderie. Brown and Levinson (1987: 103) emphasise that claiming common ground does not necessarily need to be used only to overcome face-threatening acts, but they are also “social accelerators”, where speaker suggests that he/she wants to be more intimate with hearer. The aim of the paper is to show how the members of several Internet communities in a self-compiled corpus claim in-group membership via using in-group markers, such as topic-related nicknames, diminutives and personalised address forms playing a major role in turn-taking and addressivity; terminology and special jargon related to the context of the discussion forum with a special emphasis on acronyms; collective and individual generic names; and the inclusive we.