lets say I copy article from a different website onto my website, but on this article underneath it if I leave comments and feedback and my opinioni on the article, will Google still consider it duplicate?
As far as I know, it's not considered to be as a duplicate if you would give credit to the author name or put the link of the source along with it. But if you want to leave some comments or feed back, I think you need to quote the article and put the link of the source where you got it.
The article will still be duplicate and your site will always appear after the original article site in search engine..
Why don't you rewrite the main article? So you'll create a unique content for your site that will be interesting to read. Yes, it takes time to rewrite the article but it bring good resuts
I think it will be duplicate. The best way to avoid it is to make sure you rewrite most of the article (or write your own of course)
it takes too much work to rewrite the article, I thought that if I give my opinion and feedback on the article that won't be penalized. Because I have seen other websites do this and they get good ranking