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I would personally take a different tack on it since the topic is copycat murders and call it some kind of play on Jack the Ripoff. The article even has a bit that says, "If the original killer is still around, don't expect him to be pleased", which sounds like exactly what's going on here.
I generally think of Irritation Is the Sincerest Form of Flattery to take a very different form, where Charlie admires Bob, and so imitates Bob in every fashion (clothes, hairstyle, interests, manner of speech) and it annoys Bob because of the incessant copying. It's not just like, Bob plays basketball and so Charlie decides to also take up basketball.
Also, for the record, Sincerest Form of Flattery is not (currently) a "trivia entry". It doesn't have the trivia box at the top, nor is it in the Trivia index. Seems like it ought to be, though.
Edited by KD

I've got this example that could fall under either Sincerest Form of Flattery (at which it would be in-universe, since that's a Trivia entry) and Irritation Is the Sincerest Form of Flattery. However, I'm not sure under which it qualifies best.
Problem is, it's stated in the page for Sincerest Form of Flattery that any related in-universe example should go under Irritation Is the Sincerest Form of Flattery, yet Hoffman didn't look up to or praise John at all with his copycat murder. Tropes Are Flexible might be in play here with either entry, but there's no proper description regarding them on the Administrivia page. So, what's the exact difference between the entries and under which could the example fit best?