I see your points. Indeed in many times I didn't think carefully before leaving a comment, and not even noticing that my comments can be offensive afterwards. I apologize for all those cases and I'll be more careful when interacting with others in the future.

@Xavier: I'm gratitude for your patience on taking so much time explaining what I've done wrong. It's an invaluable course.

Let me change the title of this issue first. That will make it more moderate and also clearer.