This doesn't seem to come up often, but it did happen recently, so I figured this would be a good time to bring it up.
On the one hand, we want answers to be inclusive, complete, and (usually) not short. So, if there is a particular topic with three relevant Bible passages that cover different aspects of the situation, I would think that we want an answer that includes all three and exposits on all three. At this point, the answer would be complete in the sense that all the Biblical evidence has been included.
On the other hand, someone else might have more information, such as a commentary or two. At this point, they may not want to repeat information that is already found in a slightly older answer so as to avoid the appearance of copying someone else (especially with an eye towards rep gain), even if the "copied" bit is properly attributed. However, as stated above, I think we would prefer a more complete answer that includes or summarizes the Biblical evidence and includes the commentaries.
On the one hand, inclusiveness and completeness.
On the other hand, the appearance of copying and mooching off of others' work.
So, which one do we want? Or is this a false dichotomy of some kind and there is a better, third option?