Back to the original topic – I think that some adcoms do read the forums, or at least look through some threads.
They most probably are aware of gmatclub existence, to begin with. Remember, in the apps we have this marketing section – where did you learn about our school etc; and there’s a list of some online resources as well to pick from. Perhaps some app forms even mention the gmatclub; I don’t know. Also, I guess some people click on the b-school links in our threads, and if they analyse the logs later, they see which site gave them these visitors.
However, I seriously doubt that they’ll be wasting their time trying to figure out a particular applicant on the forums. I think they read our posts for general purposes mainly – i.e. estimate the quality of the applicants, see how their school is perceived etc.