Add the ability to mark an answer as incorrect
Give the OP the ability to indicate that an answer is not an acceptable answer. That is to say, even though an answer might possibly contain accurate, factual, interesting and/or valuable information, the PO may want to indicate that for whatever reason this answer does not answer the question and will not be accepted.
As part of this feature, the answer count shown on question lists will not include any rejected answers. For example, if a question has three answers and two of them are rejected, the question will be displayed in lists as having only one answer.
This will address the problem where an OP gets an answer that s/he feels doesn't answer their question, but the question appears on lists (like the interesting questions list) as having an answer. When that happens, many experts who might otherwise look at the question to see if it needs an answer will skip over the question because they think it already has an answer.
Note that rejected answers should be left visible because they may contain very good information. If it is the case that a rejected question could be edited after being rejected, then the OP should have the ability to un-reject an answer that does answer the question after an edit.
I ask for this feature on behalf of an OP who asked me to delete my answer because (1) he thought it didn't answer his question and (2) it was keeping people from looking at his question.