In this question the solution to was discovered after some discussion in the comments fields. Should the answer be updated/edited to reflect the correct solution? Or should another answer be posted?
The answer should be edited to reflect the correct solution. Usually when you mark an answer as accepted, the normal tendency is to only read the answers and most often, you skip the comments (my own experience, need not be true always). Hence I think the answers should reflect the correct solution.
The above solution would be assuming the comments are on the answers given to that question. However, if the correct answer is discussed in the comments in question itself, then a new answer should be posted by the one who gave the answer. If not, then the OP can himself give the correct answer mentioning the person who gave it in the comments to really give him due credit.