I read the Slashdot FAQ on the Friend/Foe system, but I still don't understand it. Is the idea just that it lets you filter a comment thread to emphasize comments written by people you're interested in (friends)? Does it hide the comments of foes?
The impression i have is that it gives fores a personal -1 on their comment score. So unless they get some +1s from others, or you have set /. to show everything, they will vanish below the breakpoint.
Note though that anyone can look up who has them flagged as foe on /..