I was disappointed that he tried to fill the void with superglue. And then tore off the handle. I would have tried shellac stick, it can be used to mimic figured grain by using different colors much the same way the damascus is done. Otherwise I'd consider inlaying a design in silver or gold or ivory or mother of pearl or something. That would make it seem intentional, it could also be a counterpoint to the single rivet. He could have cast a small decorative concho or whatever you call it.
Just my .02 as a creative problem solver who hates to do things twice.
Since I am an attention whom are, here are some photos of my knife made about 16 years ago.
The steel is from a coil spring we scavenged at an auto junk yard. We used leaf springs for wood turning tools and froes and axe heads and such. the coil spring was straightened and flattened then roughly shaped, and sandblasted. There are still a lot of files marks and grinder marks.
The guard and pommel were first made in wax and then cast in
Brittania Metal which I then dimpled with a tiny ball peen hammer that I made out of a grade 5 bolt that I ground and polished.
The handle is from some walnut from a 200 year old tree that that was cut down to make way for a hospital. My teacher and his friend brought a chainsaw mill to the building site and took away most of the trunk. A friend and I got to keep some of the larger branches (8-12 in diameter) I still have some of it sawn into bowl blanks. I just expoxied or bondo-ed the handle and pommel on.
I have no idea of the rockwell hardness but a file has to be pretty new and sharp to bite the steel. After looking at Wheeler's process I see how I did a lot of things out of step causing me problems later.
Maybe I will sharpen it. The handle is a bit slim for my hand.