On the bottom right of every post is a + , a - & the post total . If you are impressed etc about a post , you can give a positive , if it annoys you or think someone is being a butthead , you can give a negative . If it does now motivate you , you don't vote . On each members profile , the total after adding the positives & the negs from all posts voted on is listed . I think it benifits as to letting a member know how they are coming across . IF they want to be viewed that way , they do nothing . IF they don't want to be viewed that way , they adjust .
Pro , asking the 3rd question seems like it is repeating the 2nd , but anyway ... it is a measure of how posts of that person has made others feel , good - bad or in between . It can signal they had a major problem with 1 person who is dedicated to smearing the reputaion of that member because they think they were done wrong & want to warn others . It can also be taken as that member annoys many others by constantly doing things frowned on . It gives some imput of the collective forum in other words