On E2 they do this with C!s (also known as cools, chings, or ching!s). Level 4+ users get a certain number of C!s along with their votes. A C! confers 10 XP on the author of the chinged node (if I'm not mistaken), and is listed even if the reputation is not. They just recently added a list of who chinged each node to the node.
Update in reponse to thatguy: FYI, so far there is no antiC!. Thus C!s can only be used positively.