Why censor people who are trying to help you?

• If their answer is incorrect, others will correct with constructive feedback.
• If their answer is rude, inappropriate or otherwise trollish, the Node Reaper will save the day.

Put yourself in position that you propose everyone should be put in...

You post what you perceive to be a good and useful answer. You feel happy that you tried to help by giving back to the community . Then one of the following happens:

• The post gets deleted and/or marked as a "bad answer" by the person who asked the question. You either:
  • Get upset and think "sh*t;, if the person knew enough to mark it as a bad answer, why the $!*%& ask the question??"
  • Take it personally and restrain yourself in the future from trying to help.
    
    
• The post is replied to and is corrected (hopefully politely) by other users.
  • Everyone who sees the original post and its corrections benefit.
  • Others who may have been making the same mistake take note.
  • Heed the corrections, improve your own coding skills, and happily move on trying to help others.

It doesn't sound like a beneficial proposal from this standpoint, does it.

Also, I disagree with your "Simple downvoting does not seems enough to me" comment.

IMHO, downvoting in the case of someone trying to help (even if it's an incorrect answer) is not just cause for downvoting. Incorrect answers should result in a /msg to the author letting them know about the mistake or a constructive reply to their post. I only downvote when people abuse, slander, or are intentionally giving bad information (e.g. "rm -rf will fix your problem").

I can see of no good reason for this kind of censorship, and hope that it never comes to reality.