Those saying that no good forum uses the like button, take a look at Westeros, which is what I'm really basing this on:
http://asoiaf.westeros.org/
Here's a relatively spoiler-free thread (though if you want to avoid spoilers completely, just look at the bottom right of the posts); http://asoiaf.westeros.org/index.php/topic/63913-abbreviation-translation-for-n00bs/
Here's a great example with both upvotes and downvotes:
http://www.zam.com/forum.html?forum=21&mid=1200547619179458414
But that's very risky.







