If I understand what I've read about it, it's butter flavoring that has it, and you have to inhale a whole lot of it. An occasional whiff of butterscotch or something isn't a big deal. There are a lot of things that are safe in small amounts, but dangerous in large amounts.
You have not read all the other threads, so this is not true information. It is contained in several flavors...butter, butterscotch, caramel, and tiramisu to name a few. And they have not been able to determine a safe amount to inhale. And there is a huuuuuuuge difference between what you inhale when popcorn cooks in your microwave and the stuff that you are vaporizing and pulling directly into your lungs. There is NO SAFE INHALATIONAL AMOUNT OF DIACETYL.