I disagree with the OP on two points.
First, although of course the point of the site is "helping people as best they can", I think he is wrong to characterize certain types of answers as going against that. The answers left on this site help people in two different ways: first, they help the person who has posted the question (the OP). Second, for ever after they stay freely available and searchable so can help arbitrarily many other people as the years roll by. The first reason is the more proximate, definite one, but the potential value in the second reason is almost limitless. So I think both need to be respected and evaluated when one looks at the worth of answers.
There are important site mechanics protecting the OP. Namely, the OP herself chooses an answer to the question, and that answer gets displayed first, no matter what its vote total. Further the site keeps track of unanswered questions. Everything is set up so that people will continue to give answers until an answer is given which is satisfactory to the OP.
However, often there is more to say about a question than the OP needs or wants to hear. In fact I would say that this is a decent definition of a "good question" on this site, and in its complete absence there is the danger of a question being "too localized". A lot of OP's here have fairly narrow goals -- in fact, it seems that a fair percentage of the questions asked here are simply homework problems -- so that a more ambitious or intellectually curious student of mathematics would want or need to read more than the minimal answer that satisfies the OP.
Thus I think that it should be unquestionably okay to leave answers which are more pitched at other readers of the site than the OP. Of course there are issues of balance and judgment involved here: e.g. if someone asks a calculus-level integration question then an answerer should think twice about leaving an answer involving the Lebesgue integral and would do well to explain the point of an answer which is so far above the level of the question posted. If you think that you are leaving an answer which is going to be over the head of the OP -- especially if there is not already an answer to the question at the OP's level -- then I think you should indicate this clearly.
Second, I looked at the question linked to in jameslmore's post...and I didn't find anything like the "over the OP's head" answers I was expecting to find. There were five answers, and they all looked pretty reasonable to me. One of them I found a little sub-par expositorily -- e.g. it used the word "primitive" without explanation; that word is no longer used in most American calculus courses so most students wouldn't know what is meant -- and I left a comment about what I thought was an unfortunate word choice. But it was certainly a good faith answer addressed to the OP. If this is the answer to which jameslemore refers to when he mentions "obfuscation", then I think that is a rather unwarranted and uncharitable accusation. The person who left that answer has left more than 600 other answers. You really think he's not trying to help people out as best he can?
Finally, where's the victim in this particular crime? The OP has accepted an answer -- which was, by some remarkable coincidence, left by jameslmore -- so presumably was satisfied by at least one of the answers given.