It is only partially obscured just like any other content that would overflow in a side column it will be clipped because the side columns have css to hide the overflow.
However it is mostly still visible and still quite usable.
In any case it is not bug but a css issue that can be solved by css. Most of the artisteer skins have this in the style-artisteer-overrides.css
.leftside , .rightside{ overflow: hidden;}
if you don't like that behavior you can easily change it, but without that when content that is too large for a side column is used it will overflow.
My advice would be to not use ratings in a side column if it doesn't fit, or else make the side column a little wider so it does fit.
Best,
Joe