Imagine this situation: I posted an answer to a question. After some time the OP decided he needs a better answer or more attention and decides to put a bounty on his question.
Now I want to add a - possibly better - different solution to the question. What do I do?
- Merge it with the existing answer. Then I am not eligible for the bounty (at least not automatically), since the answer was posted before the bounty was in effect.
- Add another answer. While I would not normally do this, the system allows it. I'll be eligible for the bounty, even when awarded automatically.
- Delete the existing answer and post a new answer (maybe with the original answer merged in it). I lose all reputation points gained from the deleted post, but am eligible for the bounty.