Fret Markers
Instruments- discuss specific features, luthiers, instrument problems & questions
Yes, you can have fancy decorative inlay work on a fretboard. And you can also have fret markers. Those are clearly two different things.
Obviously, decorative fretboards are pretty. (Don't we all love that long-stem red rose on the Blue Lions?) And if the decoration varies up and down the fretboard, then it might serve the purpose of fret marks, but only for the owner. Anyone else grabbing that instrument for the first time would have no idea what's going on. That's why there are standards. The standard fret marking pattern of 3, 5, and 7, means that I can borrow anyone's instrument--or switch among the several that I own--and know at a glance where I am on the fretboard, even if there are one or two extra frets. That obvious advantage cannot be overstated. If one of my instruments were marked at 3, 5, and 7 and another at 2, 4, and 6, and another at 1+, 3, and 4, those fret markers would lose their purpose and would have to be ignored altogether. They would confuse rather than clarify.
So that brings us back to the original post, which was about the proper placement of fret markers, not decorative inlay. An individual player can request fret markers anywhere s/he wishes. Fret markers do not change the sound of an instrument. But anything other than the standard pattern would confuse anyone else. I would strongly urge luthiers to either use no fret markers or use the standard pattern, unless, of course, they are responding to a specific request for a custom dulcimer. And again, for a diatonic fretboard, there is no need for fret markers anyway since the pattern of whole and half steps tells you exactly where you are on the fretboard.
I personally would not be able to play with raised fret markers at all. As you slide from one chord position to another, you need the fretboard to be as smooth as possible. And even when not sliding, you want your touch on one fret to be identical to the touch on another fret. There would be no way to play with any speed with an inconsistent touch on the fretboard. There is a reason why everyone uses inlay both for fret markers and for decoration.