But I don't think the idea that Snape never killed anyone, for instance, goes against what I'm saying. I actually think that might very well be true, that neither Snape nor Regulus ever killed anyone (except Dumbledore). But I think that's different than explaining away the things that we do know about him. I don't want to assign any crimes to Snape that we don't know about--we've got no canon for him killing anyone besides Dumbledore. He can't be blamed for any specific DE crimes except being the eavesdropper, which appears to have led to him doing something to make that right. To regret joining the DEs, he has to have joined the DEs for some reason.