It isn't confusing, there is already a thread for guidelines on how to make a quality post. If you are interested here is the list(the last link is a technique to make your post look better):
How to make High Quality Post
Yes. Useful. and why is it still not optimal, I think that's still normal because each person also has their own individual guidelines regarding different word limits, format and tone and what to write in their posts. Even if the delivery is felt to be lacking or something else, someone will respond to contribute and not leave the discussion.
That's right, it must have meaning, be original, have regular words, be simple and easy to understand and have content such as subject, predicate and object.