User blog comment:DaNASCAT/Technical Update: October 21, 2015/@comment-24473195-20151021211133

"The special syntax highlighted editor currently used on portable infobox pages will be rolled out to all template pages, to give a consistent user experience."

Finally!

I for one won't miss that annoying editor that keeps wrapping everything and making it extremely hard to understand even the simplest templates. Perhaps this will force contributors to be more mindful when creating big walls of texts and crazy templates.

The ace editor is incredibly flexible and powerful, and as noted before has a lot of hidden functionality that caters to basically all contributors. It includes theming, line wrap options, macros, keyboard shortcuts and so much more.

Hopefully this will lead the way to a proper content handler for pages, it would be nice to have custom syntax highlighting for json, xml, and other pages. This is already possible, through the tools available in the ace editor, but it doesn't have the option to disable saving pages with syntax errors.

Also, any chance of backporting this fix? :

https://gerrit.wikimedia.org/r/#/c/160367/

Note: A little known quirk of the ace editor or mediawiki is that once it reaches a particular size ( roughly 80kb) the text will simply be invisible. So be prepared to receive some complaints about "invisible templates".