OK...
I have a blank Filco, and the keys are going shiny, after not alot of use. They arent coated, but it seems the fast wear is more a result of the texture of the plastic rather than the coating.
All keyboards are prone to wear on the keytops, it's just harder to see on some models, and some models are more resilient than others. For example, an IBM Model M has a very rough texture out of the box, and the beige goes a long way to hiding shiny keys.
I do know that EliteKeyboards sell 104 key sets of blank keytops, though I'm not sure about 105 key sets.
As for the HHKB, programmers and terminal nuts like it because they use the keyboard ALOT more than your average user, who is far mor mouse reliant. The HHKB is built around the concept of keeping your fingers on the home row, and this shows, with even the arrow keys being moved onto the main block. The lack of a numpad isn't really a problem, as most numbers in programming aren't that big, and are few and far between for the most part, making it faster to use the top row of numbers, rather than have to move your right hand to the numpad.