Yeah well you'll see gifs repeated a bunch, that's just happens with gifs, because they get rehosted a bunch of times on imgur and the automated filters don't recognize it. But a lot of subreddits overlap (r/gif, r/gifs r/reactiongifs, r/videos sometimes) and you just have to kinda expect to see crossposts between them in those cases. If you do see the same gif in in the same subreddit, then in that case it is a repost, but anyone who claims that they created something that they did not, especially when it was already posted on reddit, deserves to be called out on it, cause that just isn't cool. Also if you are relatively new might I reccomend the excellent browser extension Reddit Enhancement Suite, (if you arent already using it) it allows you to open images within the page like you can with text posts and video's so that you don't have to go to a new page just to see the image. It makes browsing gifs much less cumbersome. (as well as many more simple yet effective usability tweaks).