Some people get away with it their whole lives. I mean, the guys DL'ing close to 1k pounds are doing it with an over-under grip and seem to be healthy (atleast as far as the musculoskeletal system is concerned)
It really sucks to say this, but there is no concrete answer. Tread carefully and see what happens...I DL'ed very heavy weights before i really started having problems, but once i got to over 400 pound DL's i would tweak my back every so often, then hurt it so i had to take a month off. Start again, work up to 400+ pounds, tweak, tweak, injure. After a point i said enough is enough, i have a whole life ahead of me with goals that are separate from BB'ing so nowadays i make sacrifices in regards to strength/size to stay healthy and achieve my other life goals.