UPvote = 100% agreeing (and a little smile mixed in for good measure)
I think the reason for the smile "UPvote", at least for me sometimes, is being you have just given that person another kick of motivation. If you keep posting and posting and nothing..., nada... zilch. DO you keep posting? But if someone gives you a "smile" (aka UPvote)... it boosts your determination and can help being a new level of "I GOT THIS" thinking.
Is that smile UPvote a false hope? No... I know I have received these kinds of UPvotes in the past, maybe even today, and I'm okay with that. Every vote keeps me striving for more.