Some forums have a "Thank" function. The other forum I frequent, XDA Developers (focusing on Android hacking/development) uses this. There's no "downvoting" or negative feedback. You might think Bladeforums is big, and it's certainly the largest knife discussion forum with nearly 300,000 registered members, over 19,000 of which are "active", but XDA dwarfs this with nearly 7 million members, 359,000+ being "active". Plus all their forums are visible without logging in and searchable via google, so there's countless more that merely read without actually signing up. Anyway, the "Thanks" system works very well there. Perhaps it's due to the sheer amount of members, but outside of individual device forums, there's not much in the way of "cliques" where members artificially inflate each others' status levels by throwing around arbitrary "thanks" (although, to some small degree, it certainly happens). More importantly, anybody can see who "thanked" whom on individual posts, and see every individual "thanked" post for any given member. Perhaps most importantly, it can be disabled on a forum-by-forum basis. The "OT" (which is far more tame than our W&C/Cove) section at XDA doesn't allow "thanks ", so any "rep whoring" type threads are easily culled.
This sort of system might work here, but I can certainly see it getting abused like the reputation system was before (which, in my shame, I was a part of). And naturally, after the failure of the reputation system, any similar type of thing probably won't be implemented. Too much opportunity for abuse.