in reply to
why a nodelet can be kept agains author wish?
Just to add to what Tye said so well- the mistake that one person makes will usually be thought of by a number of the other readers who havn't posted, they can learn from seeing why your solution was wrong. I have noticed good instructors often will start a training session with something like "don't be afraid to ask questions, the chances are every-one else is thinking it as well".
Until you've lost your reputation, you never realize what a burden it was or what freedom really is. -Margaret Mitchell