If someone starts an attack, then you start the spell at the same time, and they kill it before the spell completes, then yes they will take the kill.
KSing is hard to punish, because GMs aren\'t always quick to respond. It seems less often that people use it as a tactic, because they know it\'s against the rules. If they do use it often, then they get off on a warning, or two warnings, and then they hide their behaviour better.
What I see more of are people who will KS once or twice, then get offline.