Solution : https://service.sap.com/sap/support/notes/1407883 (SAP Service marketplace login required)
Key words :
0 sp15 - apply patch #13 sap j2ee engine 7, correctly process utf8 encoded characters, utf8 encoded characters results, incorrectly encoded utf8 symbol, higher sap j2ee engine 7, utf8 encoded characters, 0 sp21 - apply patch #9, 11 sp4 - apply patch #5, utf8 encoded symbol, sap j2ee engine