There is a thread in the Software forum in which several trolling and offensive posts have been marked as "Helpful".  As far as I recall, in the old forum only the OP was able to flag a post as such, but now apparently any user can do it.  Restricting this facility to the OP was a better idea.
 

And, even more ironically, we can't mark your post as helpful only spam.

You can even mark yourself as helpful. It does wonders for my self confidence.

well now... if that don't beat all....
 
 
yep... the OP should only have that "helpful" button....

I don't see any particular problem either way - in an open forum every thread is a collaborative effort.
 
So you could argue,"Why should only the OP have the power to mark something helpful?". Sometimes there are genuinely helpful posts that might slip through the cracks or the OP might not appreciate them for whatever reason. Or maybe the OP is just getting good but unappreciated advice. Is marking only "bad" advice and like minded opinions really "helpful"? Differing opinions and childish arguments are sadly going to exist regardless of opposing camps marking things "helpful".
 
But it's not like it really matters one way or the other, even if it's misused or abused or whatever on occasion. Collaborative efforts are as imperfect as the collaborators are.
 
Also note that if you put your mouse over the helpful thingy you can see who marked it and evaluate it accordingly.

But...
Why can't I mark this thread "Unhelpful"?
 
 
What would be even cooler than this is if everyone could mark your post as helpful. Imagine you helpful post having a string of "Helpful" tags on it.