So, I don't think this is a bug. If it really does some matter, I tend to believe that is a question of design. Because I find it is somewhat a little complex to avoid the unknown format to be printed more than once. I want to know your opinion about it. I would be very appreciate if you can send me a reply at your convenience.
It is a bug, the output should be sensible and it isn't. Either, the output should be clearer, or it should only report that it is a unknown once.
