Here is the accompanying project.
I've nicknamed this behavior "list entanglement", although it works more like a reference that constantly updates itself.
There are two variables: A and B. Both are lists with one item. B, however, is set to A. If the item in A is set to any value, B is updated to stay the same. This behavior does not work if A and B are just strings and not lists containing a string.
I managed to come across this... thing... when I was working with a stack, and items from the stack were being modified, which wasn't supposed to happen. I thought it was maybe because I was referring to a global variable, so I replaced those references with a script variable, but it kept happening.
I looked through the reference manual to see if something like this was mentioned, but I couldn't find it. Maybe I didn't look hard enough.
Is this intended behavior but just not documented? Or some sort of devilish bug?