What are the criteria to conclude that the post is with quality?
The length? The statement? The point? The credibility of the writer? Or is it just upon the discretion of the reader?
If you look at the very definition of 'Quality' then you will get your answer.
the standard of something as measured against other things of a similar kind; the degree of excellence of something.
From that you can see that quality is a subjective thing. Before posting ask yourself something simple like 'is this post adding any value to the discussion or not?' - if the answer is yes then in time you'll gain merit, if not, don't post.