The one thing that the friend/foe system missed IMHO was the ability to tag posters with comments like "suspected oil shill" or "actual Intel chip designer" or stuff like that. That's often more useful than some vague idea that a poster had some especially good or poor posting in the past.
The RES browser extension does this for Reddit (which I suspect you might already know, but others might not). It also sort of does automatic friend/foe for you, as it displays the net number of votes that you've given to each user next to their username, turning bright green for positive numbers and bright red for negative.
