If a perfect copy is no longer "you", that means if the many worlds interpretation of quantum mechanics is true, the universe is splitting into copies unfathomably many times every microsecond. That means this universe, and by extension you, are almost certainly not the original anyway. Why would one more instance of that matter?
The many worlds interpretation of quantum mechanics doesn't mean this, even a tiny little bit. Even if it did it's silly to make decisions based on the hypothetical implications of an unfalsifiable interpretation.
Well, it think it's the fact that you'd ending your current copy by ripping yourself apart at a molecular level. Like, I think the many worlds interpretation is correct, but that doesn't mean I'm gonna blow my brains out because there are infinite versions of me.