Interesting, the term 'advocato' doesn't yield much in the terms of research along these routes, do you have a paper reference? (Lori Avocato does have a few papers that pop up on scholar.google.com though, I bet she got kidded a lot in grade school)

So perhaps the ideal karmic feedback device for this system is a compass rose with a center button. This would be

                <agree>
                   |
  <not this> - <perfect> - <more this>
                   |
               <disagree>

The idea being that you could choose 'perfect' (which would exclude all other choices) or you could choose one of agree/disagree and one of not this/more this.

The idea of course is that there is an inferred 'commonality' point and by dropping these comments and stories you can have people give an indication of where they sit relative to those inferred points.

And while it certainly might lead to a bunch of 'echo chambers' my experience in such systems is that it pulls people out of those echo chambers into bigger clumps than that.