I'm going to stick this one here and try and stay out of the discussion! This is one for the community to decide upon and deal with whatever the decision should be. Should the maintenance of a formal list of accepted 'inaccessible tiles' be agreed upon (or another method) then I'm more than happy to integrate that list into the site but I'm going to let someone else do the maintaining of the list itself. How you decide what should qualify as an 'inaccessible tile' is also up to you. Also how those are shown in the leaderboard is equally up to you ?