My memory might be fooling me, but I believe I have seen comments or discussions an meta regarding this matter. I am unable to find it now, so I will ask about your opinion.
If I answer some question and then it shows up that this answer is incorrect, are there sometimes reasons for not deleting an answer?
I can personally think of some situations like this:
This would help other answerers to avoid the same trap. (E.g., if there is one very "obvious" way to solve the problem, which is for some "not so obvious" reason wrong. Such situation could be a reason why similar incorrect answer will pop-up several times, after the preceding one is deleted.)
There is some information in comments, which I consider interesting and it would get lost by deleting an answer.
The question was misunderstood, so it is answer to a different question. But since I invested time into writing the answer and I find the information I've given in it interesting, I am not too keen do delete the answer.
I did not list partial answers here, since I believe they are ok. (At least for questions which, in their formulation, have several more-or-less independent part. Or for difficult questions, where we are only able to give partial answers.)
So are the above reasons sufficient to keep the answer? If not, how could the situation in cases like 1,2,3 be resolved?