Based on: a Greasemonkey script to place a border on the side of comments on MetaFilter sites that have been favorited multiple times, with the ability to specify the minimum threshold
In threads with more than a few comments, I'd like to see highlighted the comments that disagree with what the original writer has said. Naturally it will be hard to find that out using semantic parsing. Or will it?
OpinionCloud uses browser plugins to gauge sentiment about individual items
Hypothes.is proposes software that will capture 'stance' (item #2 at about 3:10 in their "What Is It?" video)