I recently asked a question - What should I do if I have a nosebleed in the middle of a meeting? This question received at least 11 answers (2 of which were deleted).
I've read through all of the answers posted to my question, and I've noticed something: A lot of the information included in those answers seems quite... repetitive.
Do I really need all of that information duplicated? No. If someone has already said something, and you are just going to state the same thing in different words, please think twice before posting a new answer. Of course, if you are going to include more information, then go ahead - but only if you are actually including information not mentioned in other answers.
This isn't just my question - see Is it rude to ask if a pregnancy was planned? Most of the answers there state the same thing: Yes, it's rude, and possibly suggesting an alternative way to ask. But it's spread out over 10+ answers, all stating the same thing in a different way.
While Interpersonal.SE may be different to other Stack Exchange sites, due to its subjectivity, that doesn't mean that it's suddenly turned back into a discussion forum. If someone has already said what you want to say, don't post a 'me too'. Doing so can get annoying, and unnecessarily duplicates content. This is why we close questions as duplicates - to make sure that content is condensed in one place. To avoid having it spread it across lots of different posts.
Note also that there is a difference between when two or more people were writing a similar answer at the same time and when the duplicate answer is posted after the second person has had ample time to read the first answer. In the first case, I do not think that they are a problem in the first case.
So what should we actually do with late duplicate answers?
Well, this has been raised several times on Meta.SE I happen to like this answer to How to deal with duplicate answers posted long after first answer(s), personally - which suggests the flagging and deletion of such answers.
This will help to keep the site from being flooded with useless duplicate answers, and serves to discourage people from posting said unwanted content.
What do people say?
See also Vote to delete answers as duplicates of earlier answers on Meta.SE.
Summary and clarification
I'm not saying that any of the answers that I linked should be deleted. They were just what made me notice that there's a bit of a problem here. The real situation in which I'd advocate deleting duplicate answers is when someone comes along later - I'd say at any point later than two hours after the original answer was posted, but that's hardly a hard decision - and posts an answer that has the same method, and the same result, and does not include anything that is not in the first answer.
Having multiple viewpoints on a situation is great. But we don't need a bunch of answers all having the exact same advice stated in a couple differing wordings of the answer text.
Now, real duplicate answers are rather rare. But before starting to write an answer, check to make sure that you're actually adding new information to the post.