Does not seem plausible at all. The claim that the book of Allah revealed for guidance of mankind can be used in any way to harm other human beings, seems to go against the the whole ethical basis on which Quran stands. Since we know that Magic and other ‘Nafsi ulum‘ as a knowldge have had been in existence since prehistoric times, so they do not require backward Quran reading for them to take effect. It is also plausible that users of the black magic use veil of Quran to hide the true mechanism of their Magic just the way mystics use the cover of religion for some of their unbelievable acts which belong to the domain of ‘Nafsi ulum‘.