Note that any associated supporting element is not to be considered in determining a parasitic gap construction. Suppose, for instance, that a case of semigrammaticalness of a different sort raises serious doubts about irrelevant intervening contexts in selectional rules. With this clarification, the speaker-hearer's linguistic intuition does not affect the structure of a stipulation to place the constructions into these various categories. Presumably, an important property of these three types of EC cannot be arbitrary in the extended c-command discussed in connection with (34). I suggested that these results would follow from the assumption that the notion of level of grammaticalness is necessary to impose an interpretation on the levels of acceptability from fairly high (eg (99a)) to virtual gibberish (eg (98d)).
see also: WikiPedia -- Chomskybot