Almost. HN only does exact matching, so if the duplicate article varies even slightly, it would not be detected. Variations include query params at the end of a URL such as &utm_medium=...
An automatically detected article will upvote the original article.
It should be noted that moderators are well aware of this loophole, and upon repeated abuse will ban accounts. If you're just submitting what you see, don't worry. If you're submitting your articles over and over again, though, well, don't do that.
