I think the "optimistic" icon is meant to be taken as - "that's a bit optimistic", i.e. "don't get your hopes up"! So, in that reading, perhaps "neutral" is fine.
If that's what it means, you need another icon, like a unicorn, perhaps?

Rainbow is all about hope and joy and optimism and good luck and renewal. From Genesis to the LGBT movement, there's nothing neutral about a rainbow. Just sayin....
New likes are fun. I agree that useful and informative are redundant. We need a hug and a thanks.
My only minor gripe is with the "disagree" icon. Only because, IMHO, it's the only one that actually requires an explanation. If I like, love or find a post helpful or funny, it's self-explanatory. It's just an acknowledgement, a nod, a smile. But when someone disagrees with a post, I would like to know why. It actually just happened to me on another thread--somebody disagreed with a member's statement, and I kept scrolling down in search for the reason or an explanation, to no avail. This is not to say that I'm against the "disagree" button, just that, as I already discovered, it can leave the reader wondering, and it can be very confusing for a new member looking for help. Just a thought.