I've seen more than a couple of times the following phenomenon: someone asks a question, and it gets several, essentially equivalent (non-simultaneous) answers, all of which differ only in small details but which (in good cases) do not completely contain each other.
Were I the one asking the questions, I would very much prefer one answer with the union of the content present in all of those given, or non-overlapping answers, adding up to a complete one. Mostly, because having to read a handful of answers, each with its peculiar notation and so on, and then assembling the information provided in them is a quite a bit of work---specially demanding on someone who is not proficient with the content!
I don't know how this can be alleviated...
Later: a good example is this one.
(Why oh why must question titles be at least 15 characters long?