I'm normally on the BG side but I did play DB a few years during my music degree in college. I always cringe a little when I see a BG player put their fretting hand thumb over the neck or even touch the E/B strings ... To me it is a sign of not so great technique and makes for a lot of unnecessary hand movement but it is accepted. On DB I learned to play classical and my teacher told me to keep my thumb on the back of the neck, not a problem from me since I also do that on BG. But then I see a lot of punk, rockabilly and sometimes jazz player wrap their thumb around the neck ... and I cringe a little their too. I was wondering how the DB community see those technique.