Signatures do change over time. It shouldn't matter if its a pen or marker, loops and sharp crisp marks should still remain the same. Just look at the J in Jack. The bottom loop (furthest bottom point to the left) comes in on the bottom but goes out on the pen auto. The loop for the top of the J on the pen auto starts in the middle with a straight crisp line that comes to a point and then goes up, the marker is a loop right from the start. Kirby using a marker or pen shouldn't make that drastic of a difference on those 2 autographs. There are other big differences. I am not saying that they are not both authentic but I am saying that it will be tough for anyone to tell which autographs are authentic because there is no certified witness.
The other side of the arguement is the similarities. There are some so do one look at the similarities or the differences? Great topic collectingstanlee, I enjoy reading all the comments on both sides of the discussion.