This is one place where Unit Tests help nicely. If the group were using Test First, then the zealots would've had to read and revise tests before they rewrote code. They would've been able to read the test code and would've known about the business logic requirements. If they didn't do that, then failing tests would've clued them in.
Actually, I think it's important not to think of tests necessarily as "comments," but rather as "specs." This is pretty much the thesis of Behaviour Driven Development.
If your tests define what your program _should_ do, then your tests can become (a) more understandable and (b) more valuable to new folks familiarizing themselves with your code.
