A large amount of translations uses invalid formatting conversion (see java.util.Formatter). The formatting conversion d (%d) is for decimal integers only whereas s (%s) should be used for Strings.
Currently there are many translations that use the conversion d for Strings like:
The only reason why this causes no problems is because there is a method that replaces all conversion characters with s (in 1.9-pre1 it is the constructor of the dj class).
Even though it currently creates no problems that is NOT the way this should be handled as then there is no reason why other conversions other than s are used in the translations anyways.