This occurred with a personal space but I suspect it is the same for all spaces. Personal space allows general access.
1. Created a page with view/edit permission set to myself only (this does NOT show up in recently updated list for other users)
2. Added a comment on the page
3. Other user was able to see the comment link in recently updated. When clicked, it said not authorized

The purpose of having a restricted page is so that others do not see the page or even the title! However, with the comment comes the title of the page. This results in questions about the page (which no one was suppose to know even existed).