The banner is fine, that's just wrong height of osu!supporter element.
The original object has height of 12pixels and a width of 80 pixels, but osu!supporter icon dimensions are 80px x 8px (the supporter image is 68 pixels high, no idea why is that, should be 8px, looks like there is some necessary background in the supporter image)./EDIT/ it's just a padding and positioning problem of the supporter element. My bad, the dimensions are fine.
So yeah, it should look like this:
after changing to this:
fix.profileSupporter {
display: inline-block;
height: 12px;
width: 80px;
padding: 0 5px; background: url("/images/supporter.png");
background-position: top center;
background-repeat: no-repeat;
position: relative;
top: -5px;}
Works on Firefox and Chrome at least. Should be fine after this.
Anyway, we are moving to osu!next so I don't think it's a big of an issue