rating of comments on the site
I am looking for algorithm for rate comments on the site. The problem that simple -\+ system is not good, because on every site are many people that are able to do only flaming and rate comments not by it's profit, but only by like\dislike it.

The big problem that my site have a lot of holly-wars themes. So I am afraid that one sort of users would minuses others only because they don't like others.

Should I give ability to put minus for post, or only plus button should be?
A lot of people often write a lot of nonproductive posts, how I should block them by his post rating?

Should I give ability to vote for comments for everybody, of only for most adequate users, and should I markup them by hands or...? For example a am opening site, and all of users have 0 comments at start. 
rating of comments on the site
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I am looking for algorithm for rate comments on the site. The problem that simple -\+ system is not good, because on every site are many people that are able to do only flaming and rate comments not by it's profit, but only by like\dislike it.

The big problem that my site have a lot of holly-wars themes. So I am afraid that one sort of users would minuses others only because they don't like others.

Should I give ability to put minus for post, or only plus button should be?
A lot of people often write a lot of nonproductive posts, how I should block them by his post rating?

Should I give ability to vote for comments for everybody, of only for most adequate users, and should I markup them by hands or...? For example a am opening site, and all of users have 0 comments at start. 