basically, i think the choice is between a human based rating (where people give points, such as on social media "like", "dislike") or a computer generated rating system (cf. one word comments are downgraded; comments with board inserted are upgraded etc). or a combination of both. I think the latter system will be best. But it may require some programming to get it working right. [I thought too of a way to rank posts from 'esteemed commenters' get higher ratings, but then I realised this needs a kind of reference point, or it would be useless]
On the whole, I am in favour. SOmetimes I see a puzzle and think: 'hm, is this correct? how about move X? And then I have to wade through pages of comments I do not seek for a possible answetr to my question. (Although sometimes I too post a short comment as encouragement or discouragement to staff on the the level of the puzzle)
Good idea!