Firstly, I understand why Accept Multiple Answers or Split Bounty among Several Users was declined, and I even personally agree with the decision: there should be one best answer, and the system should be designed to encourage that.
However, in the case of a tie and an expired bounty, then as How does the bounty system work? and What happens if there are 2 answers with same highest number of votes when the bounty is expired? explain, automatic awarding awards (half) the bounty to the oldest answer.
I feel that:
- This encourages hasty answers on bounty questions (which are then improved by edits later).
- This encourages unnatural (contrary to what they would have done otherwise) unvote/downvote sniping to break the tie at the last second.
For those reasons, it seems to me like it would make more sense if the half-bounty were split among the highest voted answers in the case of a tie (not awarding it at all in the case of a tie would still significantly encourage sniping).