Typically, I see: This board is currently disabled.
It does not prevent me from doing anything, but apparently, we (moderators) are treated differently with respect to those messages.
When we were having the big spam problem, I created another login to test the registration screen. If I login with that user, I get the same message you described but the index page is not shown and I can do anything and cannot view any messages.
"Never give a flute player a screwdriver."