You make a valid point, but I wonder how many Mudcat users can read fully-featured solfa, with all the dots and dashes it uses to show note durations and which would be needed to convey melodies? I didn't have even the minimal voice training you did, and I can't sing "Doh mi sol" without singing the scale first top remind me of the intervals. I learned to sing a scale from doh to doh, but nothing more.

Solfa may be human-readable, but once you start adding the dots and dashes it becomes considerably less so without a lot more training. At a glance, to me that looks no easier to read than ABC (which being text can be read without the help of a computer)

Whether solfa or ABC is chosen think most Mudcat users will rely on computer software to translate it into something they can use, whether that is notation or a MIDI playback. However ABC has become the standard for sharing folk tunes and a lot of folk musicians use it, and to me it would seem odd for Mudcat to choose something different.