Taut or not, the key thing is you have to judge your rope tension by the conditions. And, you have to be prepared so that means knowing what it feels like for someone to fall into a crevasse....i.e. practice. Usually, when there's not a lot of obvious crevasse hazard, I don't really mind having the rope drag on the ground a bit.In more obvoius terrain, everyone's a bit more conscious of rope slack and you try to ameliorate it. Besides, you aren't going to stop a falling body with a yank of your hand. Only getting down and digging in will do that. So, you need to be keeping an eye on your partner, not the ground.