On talk pages that have titles starting with a full stop (period) such as [[talk:.mp]] and [[it:Discussione:.uk]] the button to launch VE is shown despite not being enabled in that namespace. Clicking on it gives the following error message:
Error loading data from server: novenamespace: VisualEditor is not enabled in namespace 1. Would you like to retry?
(incidentally this message is not translated for it.wp)
Possibly this bug has the same cause as bug 55493