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, then 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.
If you're running a private wiki (no public editing allowed) then you'll need to also set the following, but note that this means your cookie data is being sent over HTTP, so make sure you only do this if the parsoid daemon is on the localhost.
You may also like to lock down the parsoid daemon so it can only be accessed from the local host which you can do by editing /etc/default/parsoid and changing the INTERFACE setting from 0.0.0.0 to 127.0.0.1 and restarting the daemon.