imgflip.com/i/293qee
Closest that I can find on my memes. I'm not going to investigate further because he deleted his account.
His is the [Deleted]
If you look, he has at least 6 votes on his comments. At least one is from me as I always upvote a comment on my memes.
But I mean, 5 other upvotes just asking what F5 meant seems odd. Speculation isn't something I ever like doing, though. However, there was someone accusing him flat out and I'm not sure his response but he shortly quit after that.
The shoe mostly fits, and if he ever comes back and denies it, then I'll change my opinion and apologize for believing that he was an alt user.
At this moment though, I would bet he was an alt user.
I think the best way to tell is check the recent tab and make note of users getting suspiciously early upvotes every time their meme is featured. Other than that, I don't see a reason to waste time finding out alt users. You just know that they do exist though.
But yes, coincidence should not be a basis of proof, as usual.
I do know gamefaqs suspended my account for a three days because I had a few infractions. So I went to create another account to keep posting on a thread and gamefaqs said my account shares the same IP as another user and therefore cannot post until 72 hours has been up. Maybe IMGFLIP could do that to discourage alt users.