i just think it'd be another way to express your opinion. it's easier to simply click on an upvote rather than tag the person, and tell them "oh i agree". like if it's on a long string of comments and you don't want to interrupt the flow of it by telling them you think what they said is funny or that you agree with them. just a thought that i had.
Maybe yeah. I think they should give more insentives than MHO and levelling up. Maybe little award stickers that go on your profile. Like member of the month and polite award or award for being helpful with certain topics etc.
I think it would bring people even further into the conversation. As soon as an opinion is placed, everyone else's input is reduced to just a comment which can sometimes be slightly intrusive. A silent thumbs option allows people to remain a part of the conversation while not intervening directly.