The software we are using is one developed by the people behind Wikipedia: the Wikimedia Foundation. Their WYSIWYG software, called VisualEditor, has been used on Wikipedia and other famous wiki sites. It has proven highly usable and reliable.
Here is a live demo: https://en.wikipedia.org/wiki/User:Sandbox?veaction=edit
If you would like VisualEditor on your wiki, please request it on our ticketed support system (TSS): https://www.mywikis.com/tss/