1)ANSWER to "naim ": I don't exactly know how "News channels block replies", but it seems to be something like it. More generally, my idea can be used not only against spam and flood but also about off-top. It often happens that somebody asks a good question, some people give good answers, but in between other people use this topic to discuss some related questions, so the discussion drifts away... They may write wise and interesting things, but if you want to find real answers to the topic question, it's not easy to find them. So this feature could be used to filter real answers from all the other stuff. And it can be really some levels, let's say: Real Answers, Off-Top, Spam. There might be other levels and uses. And let everybody find what he or she needs.
2)ANSWER to "other users": My idea has nothing to do with Robots and Soft. Its point - "to preserve freedom": not to clean, but to single out more precious info in long topics.