Board Thread:Questions and Answers/@comment-24927975-20140830054539/@comment-25165281-20140831083110

You are spawning on the top layers of the world barrier (Invisible Bedrock) If world is Old), which results falling 128 blocks or less onto solid land, so even if you have diamond armor on you still will die. This can be prevented by building a spiral staircase up to your spawn point.