Hi Jeff,
I did create the TWc codemirror highlighter. TW5 syntax is much more complex. eg: it allows html + widgets + wikitext. All mixed together. So the new highlighter would need to be based on the cm html highlighter + the tw stuff as overlays. I did create the TWc highlighter, because at that time there was no good external editor to develop and test twc plugins. It was really painful to use plain text.
Now I'm using
brackets.io .. If I'm editing widgets or the TW UI, I just use the html highlighter. It isn't perfect, but it highlights enough, to have a better overview as plain text. ... And for the TW wikitext, I don't need the highlighter anymore :) ... Or there wasn't enough motivation/incentive to develop the stuff.
have fun!
mario