Back in 2013 OneNote was started. Back then Microsoft OneNote did not have a full featured web interface. I used that at the time and had many notebooks. I wanted a way of taking those notes with me on my phone. I had limited data and wanted an application that would sync all my notes, let me modify them, and sync them back. I tried a bunch of applications and there were none that fulfilled my offline and tree structure requirements.
OpenNote has a text only design. No icons or symbols other than ascii non alphabetical characters. The application just so happened to end up this way. It has a very clean feel to it and does not distract you. I would like to keep this going forward.
Why emphasis on text? Text is a really old medium for storing information. All sorts of style and support for it. Computers store text really efficiently in comparison to blob data like images.
The first version of OpenNote was a PHP fat application. Views were prepared by PHP and sent to the browser via a full load or AJAX.
Second major revision was the switch to the then booming Angular 1 framework and use HTML5 application manifest and CouchDB to provided offline access and syncing.
The most recent efforts have been to add modern features. Tags, markdown, and a CLI.