I've checked the ACL few times but it seems that all is set correctly that can be set. Guests can't vote up/down for question (the up/down arrows are not visible), but they can't also vote (NO ACCESS POPUP) for answers where the arrows ar visible for them - please check the attached image.
I am sorry for the inconvenience caused. I've tried to replicate this locally and seems I can reproduce it. I believe this a bug. I have already consult this with our developer and it will track it in our issue tracker.
Thanks for understanding