The social-epistemic self is constructed of language. To criticize implies a certain distance necessary for evaluation. If, however, the subject is constructed of language, and any critique will also be made of language, then self criticism becomes impossible, or at least operates without the distance necessary for any real angle of critique. Much of social construction, particularly the work of Bruffee cited here, draws upon the philosophy of Richard Rorty. The implication is that social construction taken in linguistic terms is invaluable, but not, however, epistemic.
Language permeates life and reality, but can never by itself encapsulate it.
So, if theories which posit social construction of reality entirely through the determining power of language do not coincide with the linguistic construction explicitly taking place in MUDs, then perhaps these theories do not entirely account for the construction of reality, or at least if they do account for it, they should maintain their allegiance to their existence as accounts of and not actual social constructions or epistemic. The same can be said of claims for the constructive power of MUDs and cyberspace. Certainly they will be a medium for contesting ideas and competing interests, perhaps oppressing or liberating. However, they probably won't by themselves construct the central core of people's existence. Penicillin may be more powerful than the pen for many societies.