A question about death on the island

If you die on the island and are buried, is your dead body safe? But if you died on the island and aren't buried you're up for grabs. Is that the way it works? So we'll never see Paulo, Danielle, or Carl, or Henry Gale reanimated. However, Charlie wasn't buried, and lots of red shirts weren't buried, not sure if the Dharma pit people count since they were below ground but not covered. Locke, Christian, and who knows may be controlled by nemesis, right? I'm still trying to figure out if the Nemesis has controlled more people than we thought. AND Claire, she was hooked up with Christian, but I can't decide if the blown up house killed her or not. I guess it did since she left Aaron. It would make perfect sense as to her/nemesis actions.