That does seem to be an excellent middle ground. The pseudonymity would eliminate the element self-censorship that the Techcrunch article seems to be hinting at, while the threat of banning combined with the high cost of creating a new Facebook account would (hopefully) still suffice to keep the discussion reasonably civil.

As a cryptography researcher I've come across numerous cumbersome anonymous reputation systems, but it didn't occur to me that Facebook is in a position to roll one out right now with a minor change if they chose to. The caveat, of course, is that it is centralized and controlled by FB. Whether they have the incentive to implement it is an entirely different question.