Considering what you wrote, in this case (when there’s a solid area inside of a larger painted area), I therefore propose to map the painted area as traffic_calming=island and the physical one as barrier=kerb + kerb=*.
if there’s consensus I could edit the Tag.traffic_calming=island wiki page adding this tagging schema. Let me know everyone (you can add a 
or 
if you don’t want to comment).
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