In my controller, the following works (prints \"oké\")
puts obj.inspect
But this doesn\'t (renders \"ok\\u00e9\")
render :j
To set the \uXXXX codes back to utf-8:
json_string.gsub!(/\\u([0-9a-z]{4})/) {|s| [$1.to_i(16)].pack("U")}