Make Real-Time Editing the Default

I’m missing a way to make real-time editing using RtWysiwyg the default. Is this a global setting or a per-user-setting, and where can I find it?

Note that states:

And of course if you are uncomfortable with realtime editing, you can click on the ALLOW REALTIME COLLABORATION checkbox to return to normal editing at any time and your preferences will be preserved.

This does not seem to be the case for me, though, the “Allow Realtime Collaboration” checkbox always seems to be switched off, no matter how it was set during the previous editing session.