If the answer is completely wrong, it can be edited, or deleted. It happens that a question is not clear to who answers; once the OPs made clear what they meant (e.g., leaving a comment to the answer), who answered can edit the answer to reflect what is being asked, or delete the answer if they don't know the answer.
Saying that an answer is inferior is rather subjective, and it is not quantifiable; the only semi-objective parameter is the "low quality" one reported by Community, which is then not correct in all cases. If for inferior answer you mean an answer that suggest to use a module that partially match the needs of the OP, then I would not call it an inferior answer.
Having multiple answers is perfectly fine, and it is one of the parameters is considered when evaluating a beta site. if there would be an answer for each question, Drupal Answers would not go past the beta phase.
See also Etiquette for closing your own questions.