The debug setting RenderAvatarInvisible, when set to TRUE makes the avatar mesh invisible as expected. However, it's possible for its effect to partially reset, as in the attached picture. In this picture I have an alt wearing the same avatar, and both avatars are set to invisible. Both clients are rendering the same thing. Sometimes the body is visible, sometimes the hair and eyes, etc. This sort of rebaking effect can also occur seemingly spontaneously. Possibly related to baking; changing the skin or going into Appearance mode usually causes the avatar to become visible again, and does not fix itself. Possible repro: After setting to TRUE, set back to FALSE, then back to TRUE. Parts of the avatar become visible after a moment. Other clients see the same thing usually, though there can be some lag between them "catching up." The reverse can happen too, with a FALSE setting still showing the avatar invisible. Edited to add: You don't even have to switch back and forth for it to happen. It can revert pretty much any time. Switching back and forth just makes it a lot more likely. Either way the setting should stick.