The page edit comment is lost when page restrictions are changed without changing the page content.

When a user edits a page without changing its content, their edit does not show up in the version history. This is usually a feature. However, if the user has made a change to the page's restrictions and commented on why the do it, the edit should be shown in the version history.

To reproduce:

1. Go to an edit page screen.
2. Edit the page restrictions, eg click "Choose Me".
3. Add a comment describing the change
4. Save the page.

If you look at the version history there is no record of the restriction being made.