Visual editor
I'm creating a local page for this as it was quite difficult to install so I want some of my own notes for future reference. The main page for the extension is at MW:Extension:VisualEditor.
First download and unpack a snapshot for the extension corresponding to the wiki version as usual
Install nodejs with apt, but if your repo has an older version than 0.8, then remove it and install using [curl -sL https://deb.nodesource.com/setup | sudo bash - NodeSource] using the following commands (see this for details).
Now install the paisoid package via apt.
Edit the parsoid configuration (/etc/mediawiki/parsoid/settings.js) adding a line for each wiki in the wikia that will be using the editor, e.g.
Restart the parsoid daemon and then test that you can read a page as follows
Include the extension and its settings in the wiki's LocalSettings.php, e.g.