I though the VM developers have solved this problem in VM2.0.12.
Apparently they didn't.
No it is not a CSS problem, but it is a JAVA problem, and happens when you mouse hovered the stars.
And weirdly, this doesn't happen always. It happens sometimes, but it doesn't happen mostly. It is just random behavior. Doesn't it the same in your website? If something has a random behavior, it must be a JAVA. CSS issues are usually "constant", if there is an error, it will create the same error always.
As far as i know; This happens in original Virtuemart as well. This means this is a bug in original Virtuemart.
Probably the moderator who responded you saw the "screenshot" which looks different than original Virtuemart layout, so he/she blamed us. This makes sense though, i would do the same thing :)
Do you also work in a live server? Can you provide me your website's live URL (if you have any beside localhost) and let me run some tests?
Cheers.