Modjeski doesn’t talk about the "sound" of fuses, only their electrical behavior. What the internal composition of the fuse does with the gas created when a fuse pops (if my memory serves me well. I haven’t read his Forum posts in in years), what’s it’s "high breaking capacity" (whatever the hell that is. The Hi Fi Tuning Fuse designer didn’t know either, Modjeski reported ;-), how it behaves in a DC circuit (what the power tubes in the RM-9 run on), those kinds of issues.
Yes, Modjeski is skeptical (to put it mildly) of the audible benefits of power cords, fuses, overly-expensive (define that as you wish) interconnects and speaker cables, etc. But one thing you can be sure of, even if you don’t consider him an audiophile: he is an expert at electronics, circuits, tubes, transformers (he winds his own), and, yes, fuses.
There is a great video on You Tube of Nelson Pass and Roger Modjeski giving back-to-back talks to DIY designers at the semi-annual Burning Amp Festival in the Bay Area a couple of years ago. Well worth your time to watch (and learn). Modjeski is now offering a new ESL loudspeaker of his own design and build, and a partnered direct-drive OTL tube amp that eschews the input transformer found in most other ESL designs, as well as, as it's title suggests, an output transformer. I'm dying to hear THAT combination! His little RM-10 amp is THE amp for the old Quad ESL.