This question already has an answer here:
It's happened to me twice already in the last couple of days (once here and once on one of the other sites) and I've also seen it on questions where I have not been involved, that there are guys that simply copy answers over, maybe change like a letter or so and paste it, then what happens is they get accepted because their answer is the newest has more visibility and the questioner doesn't really seem to care. As I've pointed out before, building rep in this site is not an easy task (at least not honestly).
Could there be a "Duplicate answer" flag that will prioritize precedence? so the rightful answerer can get their rep?
Can we do something about these copy pasters that take the someone else's credit?