There are badges like
Analytical ("Visited every section of the FAQ") which can be awarded to a person only once. Yet there are those that can be obtained multiple times, like
Nice question ("Question score of 10 or more"). For some questions it is clear that they can be obtained only once (usually they have "First" in the description). For others it is impossible to know without either trying to actively fulfill the requirements for the badge twice, or checking the profiles of other users (for example
Suffrage, "Used 30 votes in a day").
I believe this to be flawed UX. The badge itself must bear an indication of whether it can be obtained once or multiple times. Maybe use a different background color, or make the badge title in italic or bold-face?