[viewfromafar]

If this is to appeal to a community, there has to be some kind of incentive for that community to add their comments (content) to this site. What is it? Reputation?

In general, it could be appealing to have an open, established process for gathering public feedback on articles. It seems a scientific community would rather have their own version set up, where they could also curate content (rather than browse by category).

[akvadrako]

If the content was free and distributed this would be possible. You could start by entering data here and then setup your own instance with your own rules if it proves to be useful.

[physicsgraph]

While reputation might be one allure, getting questions about a paper answered (even if not by the author) is helpful. Pointing out fallacies or holes-in-logic in a paper might be a poor investment of time given the number of papers to comment on.

A grander vision of gathering feedback as part of a normal process seems desirable, but I don't know that the incentives for stakeholders are present to enable that.