I've noticed on Stack Overflow (and this is probably true for other SE sites) that I often run into duplicate questions that were never flagged. A lot of these questions are answered, often correctly and sometimes it's really a great answer. So I'm wondering, is it good practice to up vote these answers?
In the privileges section the following is stated.
Whenever you encounter a question or answer that you feel is especially useful, vote it up!
Now this may be true to the answer in question, but should I up vote these good questions? After all, they are to a duplicate question, and the original question may have a similar good answer.