What would you do differently if the mark was there versus if it wasn't?
ASCII is a perfect subset of UTF-8, so any operations you would do on UTF-8 are also operations you would do on ASCII. The behavior of your program wouldn't change. The BOM is a no-op when it comes to how your program handles things.
However, it has the potential of confusing older programs. It makes things that should be simple (like 'cat') need to be encoding aware, and modal. It means that streaming multiple files one after the other breaks.
So, in summary, the BOM doesn't buy you anything, or give you any important information about a file. It does make things harder.
ASCII is a perfect subset of UTF-8, so any operations you would do on UTF-8 are also operations you would do on ASCII. The behavior of your program wouldn't change. The BOM is a no-op when it comes to how your program handles things.
However, it has the potential of confusing older programs. It makes things that should be simple (like 'cat') need to be encoding aware, and modal. It means that streaming multiple files one after the other breaks.
So, in summary, the BOM doesn't buy you anything, or give you any important information about a file. It does make things harder.
It should die.