@hugssandi I am happy you are enjoying playing!  Sometimes, music just feeds the spirit. . . :)

Robin, I'm not sure I realized you are a noter only player.  I love, LOVE your playing!!!  I dream of a chromatic, sometimes, but I think I still wanna master what I have first before moving on.  And I have a long, long way to go!  I am enjoying it so very much though....

I enjoy seeing the responses, folks! 

Playing mountain dulcimer with a noter is all I know-- I enjoy it tremendously!  And there are MD players who play styles of music I enjoy yet could never hope to play.  If a chromatic mountain dulcimer is what is called for to play the music a dulcimer player wants to make, then a chromatic fretboard it must be!  :)

With both dulcimers and banjos, I don't necessarily see it as all about the number of frets or non-frets, but more a matter of the style the instrument is played in, which is usually closely connected to the repertoire (but doesn't always have to be).

I have diatonic epinettes, mtn dulcimers with one or a few extra frets, a chromatic langspil, and both (chromatic) fretted banjos and fretless banjos.  They're ALL great for doing various things- playing in various playing styles, playing repertoire from different time periods or different music cultures and genres.  Each one has its own wonderful charms.  If you have diverse taste in music, it's great to have a selection of instruments/tools to get the effect you're after!

I wonder if the same conversations, etc., occur concerning fretted and fretless banjos.

I did an experiment back when I first added a plus fret and repeated it with my first chromatic MD. I played a couple of tunes on my diatonic, then on the one with the added fret and the chromatic. They all sounded and played the same, by golly [and my other half couldn't tell the difference].    I don't use a noter though, and that can make a bit of difference because of the extra 'bumps/thump's.

I don't think it's so much that it sounds like a guitar.  The logic is basically "If you want to play a fully chromatic instrument, why don't you just play an instrument like a guitar (or banjo or mandolin, etc.) that is already chromatic?"

The purists would say that the diatonic fret pattern is a defining feature of the dulcimer.  As you begin to change one of the dulcimer's defining characteristics, the instrument is moving away from being a dulcimer and transitioning into a hybrid instrument.  Not a guitar exactly, but beginning to look and play more like a guitar and less like a dulcimer.

To get the sound of a guitar, you would need to increase the size of the dulcimer's soundbox, extend the neck/fretboard beyond the soundbox, increase the number of strings, and adjust the gauges of the strings.  Each of these changes is a movement in the direction of the guitar and away from the dulcimer.

If the only change made is to fret the dulcimer chromatically instead of diatonically, then the instrument will still sound more like a dulcimer.  However, it will have some of the playing features of the guitar.

Some Common Features of Each Instrument:

Dulcimer = Smaller Soundbox, Diatonic Fretboard, Fretboard Does Not Extend Beyond Soundbox, Fewer Strings, Lighter Gauge Strings, Played on Lap with Fretboard Facing Up

Guitar = Larger Soundbox, Chromatic Fretboard, Fretboard/Neck Extends Beyond the Soundbox, More Strings, Heavier Gauge Strings, Played with Hand Reaching Under and Around the Neck

Putting a chromatic fretboard on a dulcimer body without changing any other features results in a chromatic dulcimer.  Not exactly a guitar, but a step in that direction.

Incidentally, there is nothing wrong with playing an instrument modified from its traditional form.  Likewise, there is also nothing wrong with preferring to keep the instrument in its purest, most traditional form.  To each their own.  What you play and how you play it are decisions to be made by each individual.  Basically, if you enjoy playing it, that's all that's necessary.

I never did understand it when people say if you put extra frets on a dulcimer, it sounds like a guitar.  If you put extra frets on a mandolin does it sound like a guitar?  Oh wait... the mandolin already has extra frets!  So do banjos and ukuleles.  None of them sound like guitars to me. 

Now if somebody wants to make the argument that playing chords instead of drones makes the dulcimer sound like a guitar, well I still disagree but I can understand where they're coming from.

The mountain dulcimer and the guitar have very different timbres.  Some music, music requiring "extra frets", can sound wonderful, more intimate on mountain dulcimer (as opposed to, say, guitar).  

For centuries, luthiers and musicians have adapted instruments and styles of play for any number of reasons.  And chromatic mountain dulcimers exist in this living tradition.