Mark which badges are capable of being won > 1 time
Different Symbols could carry the information, that a badge can be earned multiple times:
(If you have a deja-vu: This question was an answer, which wasn't a real answer here).
animuson claims, that many badges are decorated with a text, which says "First ...", which indicates, you can earn it only once. That's right. But a lot of the badges don't indicate anything in the text:
And in some views, this information isn't visible - you have to hover over every badge, to see the tooltiptext, which won't always tell you, whether it is possible to receive the badge multiple times:
(Except you earned a badge already multiple times, of course).
Of course it would be some work, to change those badges, but apart from that, I don't see any drawback from this feature.