You can use the usual XML comments "<!--" and "-->" around an XML block to disable it. However, this won't work if the block to disable itself contains comments, because XML comments cannot be nested. Instead, you can use any XML tag which is not expected in the current context around the block, e.g., surround your block with "<comment>" and "</comment>". This will work even with additional such tags inside that block or XML comments inside the block. Note that this currently works because there is no structural XML validation in place.