Item's rating is not a metadata. It's at the core of the data about comments made.

Yes, it's a way to find best comments in a thread (not guaranteed, but much better than nothing).

Has nothing to do with ego.

How about if there was a glyph or color that denoted the amount of votes,views,etc? I think one of the issues was putting a numeric score on an item encouraged upvoting already popular comments.

May be some intelligent coloring would be a good replacement. I just need something that would tell me what comments are likely to be more informative.

For me, it is visualization issue. I used to be able to skim through the comments much faster. Sometimes there was a comment with tons of votes deeply nested in a thread and I would pay attention to it.