There is much snake-oil around audio equipment. I am consistently amazed at how many new ways can be found to part the gullible from their money. Directional fuses is a new one on me! I so wish I had the imagination and lack of morals to allow me to make money like this.
There is one way you can actually make fuses directional, and that's put a different size of connector on each end. You can also print an arrow on them, put a note in the datasheet, and charge 100x more than for the old bi-directional ones.
The fuse comprises 20mm of the 200km path from generator to amplifier. Mains carries RF interference on it, with added 1500v spikes. It's worth adding an RF filter, it's worth some TVS over-voltage protection diodes. Is it worth silver plating 0.00001% of the generator to amplifier circuit? I think not. I notice one of the fuse reviewers removed the fixed cord and replaced it with an IEC socket. Do you know what the contact material is on those?
A friend once asked me if there would be any audible difference between wiring speakers with 160 strand oxygen-free linear crystal copper speaker wire, or 4mm2 twin'n'earth. I said yes. If you use the twin'n'earth, you will have much more money left over to buy music.