Yes, I am getting the same with that tool. Yet, google webmaster tools reports the errors as listed at the
top of the page you posted to. Which is logical if you look at the malformed html.
Correct. But that's not the issue. Read my post at the top of the
page you posted to.
XenForo only has this rating function on a sidebar blocks. Which has multiple lines. This addon tries to stuff a multiple row design into a single row design. As such it adds 2 rows to the normal thread header, instead of extending the default row. In the default style the issue is not clear, because it all has a white background. But as soon as you have a style with a background then it becomes a mess.
Please read the 3rd post from the top of
the page you posted to. I already explained it there.