I've personally merited posts which I outright disagree with
I do that sometimes, but it confuses people:@LoyceV, meriting/agreeing to the OP from trusted device but disagreeing from non-trusted device 
Most people have been conditioned by large corporations to use "Like" and "Upvote", and they're used to it. Merit is different, but it doesn't show when you're meriting a post. Users won't know the difference if they don't read about it on Meta.
I'd say Bitcointalk needs a small explanation on how to use them ("merit good posts") on the "Merit a post"-page.