With LinkedIn, Research Gate and Twitter (there might be others I am not aware of), many people have managed to make an online presence for themselves through various activities.
Does this in any way affect a PhD admit for the indiviual?
Please assume the presence to be based on technical activities and all in a positive notion.
Most schools have an application. Your admission is based on the contents of the application.
I can't imagine a school that would then spend the extra time to formalize an additional search of information not supplied in the application to bolster the application. Perhaps an individual might do so, but generally this is discouraged by any competent staff because there's always the initial problem of "do we have the right person in the first place?" and then there's the other issue of "how do we disqualify someone based on information not in their application?"
If the information supports your admissions, it shouldn't be referenced by proxy. Put it in the application and the supporting materials requested by the school.
