It's just a minor CSS issue. See the following gif:
Looks like the problem is that there class
.bounty-vote-off, which is used to style the un-awarded bounty button when you're not hovering the cursor over it, has an extra
padding: 2px 4px 3px style that doesn't match the
padding: 0.2em 0.5em style for the
Simply removing the
padding style from
.bounty-vote-off should fix this bug.
Ps. I'm pretty sure this also affects several other SE sites besides MSE, including (at least) the recently graduated Academia.SE and graphicdesign.SE.
Actually, the real cause of this bug seems to be that the bounty icon styling on this site (and on Academia / Graphic Design / etc.) is a Frankenstein hybrid of two entirely different styles:
SOFU style (SO):
Beta style (crypto.SE):
Frankenstein style (meta.SE):
Frankly, I suspect that whoever designed these stylesheets simply started from the beta styles and tweaked them to look more like SO, but forgot to modify or test the unawarded bounty appearance.