Well, you can ask Mr Lupin but I think we're taking the right precautions so that he can't really hurt us with any information he's given. I mean, he's not going to contact Voldemort through his Mark--he couldn't do that in Saltash even if he tried. And he's not going to get a journal and start writing to people (which also won't work in Saltash). And do you think if you told him about the horcruxes and he did escape somehow, he'd go and tell Voldemort about his vulnerability? After he told you that he'd already sort of helped Selwyn?