Though I appreciate your motive, you obviously don't have a realistic expectation of human nature.  As delicately as you may have tried to couch your request, you have in effect insulted most of the posters on this site.  Now you ask them to grade their contributions from 1 - 10 with the expectation that most will be grading around a 1-3.  I would expect most of these people would consider their submission of some importance to someone or they otherwise would not have made the effort.  I agree with you in principle, that any one of us may find most of the posts irrelevant to our personal needs, but unless a post is inappropriate or in bad taste, this forum remains something of a democratic one in the truest sense, for good posts or bad posts.