1. Is importing an answer from another SE site acceptable? What if it is one's own answer? I have not seen this done before, and don't know the 'official' policy if there is one.

Adding to the other two answers, I also think that it is perfectly fine to copy another site's answer with attribution. I'd like to add though that I think it's a good idea to mark the answer as a community wiki in that case. That means that the reputation when the answer is voted on or accepted doesn't go to the person who copied the answer. The attribution link might encourage readers to go to the original site and give credit to the original author m

1. Is importing an answer from another SE site acceptable? What if it is one's own answer? I have not seen this done before, and don't know the 'official' policy if there is one.

Adding to the other two answers, I also think that it is perfectly fine to copy another site's answer with attribution. I'd like to add though that I think it's a good idea to mark the answer as a community wiki in that case. That means that the reputation when the answer is voted on or accepted doesn't go to the person who copied the answer. The attribution link might encourage readers to go to the original site and give credit to the original author.