Absolutely can't understand how anyone can even CONSIDER teeth scraping as something desirable! Having a "no teeth" experience is one the most important qualities in a good blowjob, especially for the guys who have thick cocks. Maybe some of those who think it's OK only feel that way because they've never had the scrape-free experience before, since so many cocksuckers, male or female, really give terrible head but somehow get away with it, since oral sex is often only seen as a prelude to fucking.
On very rare occasions, I have been asked to add some tooth action during a blowjob, and it just seems bizarre to me that anyone would actually enjoy it, since the quality that distinguishes exceptional cocksuckers from amateurs is exactly the absence of any scraping during the act. For true big-dicked deepthroat aficionados, a smooth, silky throat without any tooth scraping is what makes it a special, addictive treat