I don't think I would know people's motives. How do you know it wasn't just that they really liked the meme and wanted to bring it back? I've done that a couple of times. And no, I don't find it annoying at all. The opposite - when I see a meme come back that was a hit 6 months or a year ago, my heart sings for joy - almost nothing I'd rather see than that on imgflip.
However, sometimes I do get annoyed at reposts. Here are two kinds of reposts that I know annoy me:
a) reposts where people repost a meme from imgflip's front page, 2 days later. I don't know why people do this. They never do well. I try to cut them some slack and think, well maybe it's just a new user, just trying to experiment with the templates and see what works, but I really find that annoying.
b) reposts where people pretend it's original to them. I think that's really wrong. Or where they get super-defensive. My attitude is, if you're going to repost, just say "it's a repost." But the trouble is, the imgflip community is way too negative against reposts for no reason at all - so maybe people feel pressured to lie and cover it up, when they shouldn't. They should just say here's the meme, here's the original link if you want to upvote that too, enjoy (or something).
If I think of any other situations where reposts annoy me, I'll let you know.
That's really interesting to me, that you are able to make up jokes. I don't think I've ever done that in my life - made up a joke. Usually I just repeat them. I might adjust it for the audience, but I don't think I've ever come up with an original joke.