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There is zero support in the software for multiple accepted answers (it has happened on occasions due to merging but those bugs have been fixed). Requests for that as a feature have been routinely denied.
@harrymc: the "accepted->bounty" concept you're referring to only applies when the bounty offerer doesn't accept a bounty and an answer is accepted during the bounty period. It certainly doesn't mandate accepting an answer, or put any other restrictions on when / how an answer can be accepted.
