No, this is not a good idea in general.
In your example, you would be moving an answer to a ‘master question’. A master question is one that typically sees lots of traffic and lots of piling-up votes over time. That would give your answer a significant advantage over the original one over at the other location. But you are not the creater of the answer, you are merely quoting it. From a moral point of view, you ‘do not deserve’ the reputation you’re gaining.
But even if you are not copying to a ‘master question’ I think it is a bad idea. What you should do instead, in my opinion, is summarize, rephrase and attribute; ideally not just from one answer but multiple ones. In science, that would generally move such a contribution from ‘plagiarism’ (bad) to ‘review’ (good).
Side note: Over on Chemistry, every now and again an answer pops up that was copied from somewhere else on that site. They are usually downvoted, commented on, flagged for mod notice and then deleted.